Ullmann's Fine Chemicals

By Wiley-VCH

A compilation of 76 articles from the ULLMANN's Encyclopedia of Industrial Chemistry, this three-volume handbook contains a wealth of information on the production and industrial use of more than 2,000 of the most important fine chemicals, from "Alcohols" to "Urea Derivatives".

Chemical and physical characteristics, production processes and production figures, main uses, toxicology and safety information are all found here in one single resource.

• Language: English
• Publisher: Wiley
• Release date: Jan 7, 2014
• ISBN: 9783527683598

Book preview

Symbols and Units

Symbols and units agree with SI standards (for conversion factors see page XI). The following list gives the most important symbols used in the encyclopedia. Articles with many specific units and symbols have a similar list as front matter.

Conversion Factors

Powers of Ten

Abbreviations

The following is a list of the abbreviations used in the text. Common terms, the names of publications and institutions, and legal agreements are included along with their full identities. Other abbreviations will be defined wherever they first occur in an article. For further abbreviations, see page IX, Symbols and Units; page XVII, Frequently Cited Companies (Abbreviations), and page XVIII, Country Codes in patent references. The names of periodical publications are abbreviated exactly as done by Chemical Abstracts Service.

Frequently Cited Companies (Abbreviations)

Country Codes

The following list contains a selection of standard country codes used in the patent references.

Fine Chemicals

Peter Pollak, Fine Chemicals Business Consultant, Reinach, Switzerland

Raymond Vouillamoz, Granois (Savièse), Switzerland

1. Introduction

1.1. History

The roots of both the term fine chemicals and the emergence of the fine chemical industry as a distinct entity date back to the second half of the 1970s. As an illustrative example, the US/UK pharmaceutical company Smith, Kline & French (now GlaxoSmithKline) was overwhelmed by the success of its new anti-ulcer drug Tagamet (cimetidine), the first representative of a new therapeutic class, namely, H2 receptor antagonists, which inhibit gastric acid secretion and prevent stomach ulcer. As the demand by far exceeded SKF's in-house production capacity, third-party chemical companies with capabilities in organic intermediates manufacture were approached for custom manufacturing parts of the cimetidine active ingredient. Lonza, Switzerland, became the main supplier of precursor fine chemicals. In a similar way, Fine Organics, UK became the supplier of the thioethyl-N′-methyl-2-nitro-1,1-ethenediamine moiety of ranitidine, the second H2 receptor antagonist, marketed as Zantac by Glaxo. Other pharmaceutical and agrochemical companies gradually followed suit and also started outsourcing the procurement of fine chemicals.

In the 1980s the fine chemical industry developed rapidly. The first multipurpose plants designed purposely for custom manufacturing came on-stream. In the case of important projects, engineering and financial support by the customers was not unusual. The latter often were Anglo-Saxon pharmaceutical and agrochemical companies, which both had a large demand for fine chemicals and were prone to outsourcing.

In the 1990s the industry benefited from strong demand. The pharmaceutical industry launched a large number of new proprietary drugs. The record year was 1997 with 53 new drug launches. The emergence of generics expanded the customer base. The agrochemical industry launched a new category of highly active, low-volume products. Lacking in-house production capabilities for the production of these sophisticated compounds, it turned to outsourcing. Management had to cope with rapidly increasing regulatory requirements. In production, tight operating guidelines, the so-called Good Manufacturing Practices (GMP), were imposed by the U.S. FDA. As a result, a kind of standard, cross-contamination-proof, multipurpose plant for the production of complex pharmaceutical fine chemicals (PFCs) with molecular weight up to 500 became the state of the art. The observance of more severe legislation regarding safety, health, and environment necessitated infrastructure expansions, e.g., for waste incinerators and water-treatment plants.

In the early 2000s the irrational exuberance of the nineties came to a sudden halt. An unfortunate coincidence of sluggish demand and the emergence of many new plants, particularly in China and India, led to overcapacity, which, in turn, impaired the profitability of the whole industry.

In terms of process technology, biotechnology unlocked promising new opportunities. In conventional small-molecule synthesis, biocatalysis enables both more economical and more ecological production processes. For active ingredients for the emerging biopharmaceuticals, demanding mammalian cell culture technology is needed. The production of these very expensive (> $10⁶/kg) high molecular weight fine chemicals requires special high-containment plants.

1.2. Definition

Fine chemicals are complex, single, pure chemical substances. They are produced mainly by traditional organic synthesis in multipurpose plants in limited volumes (< 1000 t/a) and at relatively high prices (> $10/kg) according to exacting specifications (see Table 1.). Biotechnical processes are gaining ground. Whereas the delineations between commodities and both fine and specialty chemicals are clear-cut, the transition between commodities and fine chemicals is gradual (see [[1], p. 4]). Fine chemicals are used as starting materials for specialty chemicals, particularly pharmaceuticals and agrochemicals. Custom manufacturing for the life sciences industry plays a big role.

Table 1. Definition of fine chemicals.

The class of fine chemicals is further subdivided on the basis of

1. The added value or degree of sophistication. It extends all the way from small or low molecular weight (LMW) to big or high molecular weight (HMW) substances. The former are conventionally called building blocks, unregulated and regulated intermediates, and active ingredients. The latter comprise inter alia proteins and nucleotides (see Section 3.2).

2. The pharmaceutical industry distinguishes between drug substance, which is the active ingredient, a fine chemical, and drug product, which is the formulated, finished drug, a specialty.

3. The type of business transaction, namely, standard or exclusive products (see Section 6.1).

2. The Fine Chemical Industry

2.1. Overview

Within the chemical universe, the fine chemical industry is positioned between the commodity and specialty chemical industries, which are their suppliers and customers, respectively. Among the customers, life sciences, especially the pharmaceutical industry, prevail (see Chap. 6). Fine chemical companies represent a wide variety of several 1000 enterprises offering mainly products and services along the drug supply chain (see Fig. 1). They extend from small, privately owned laboratories all the way to large, publicly owned manufacturing companies. Large Western fine chemical companies still dominate in sales revenues. Most of the small ones are located in Asia, particularly in China and India.

Figure 1. Drug development stages (HTS: high-throughput synthesis) Source: Lonza

A comprehensive list of about 1400 fine chemical companies (including traders) can be found in the event catalogue of the CPhI exhibition [2].

The main raison d'être of the fine chemical industry is to satisfy the product and process development needs of the life sciences, primarily pharmaceutical and agrochemical industries, and other specialty chemical firms. It has its own characteristics with regard to finance, R&D, production, and marketing. The R&D expenditure is highest within the industry. Its main task is process development (small r, big D). Production takes place in asset-intense multipurpose plants.

Depending on their specific activities, one distinguishes three types of fine chemical companies, namely fine chemical/custom manufacturing companies (CM or CMO), contract research organizations (CRO), and laboratory chemical suppliers.

2.2. Fine Chemical/Custom Manufacturing Companies

Fine chemical/custom manufacturing companies are active in process development, scale up, pilot plant (trial) production, industrial-scale manufacture, and marketing. Custom manufacturing or its counterpart, outsourcing, has remained the most important discipline of the Western firms (see Chap. 6). Due to their advantage of low costs, the Asian companies have a strong position in active ingredients for generics [3].

Despite some consolidation, mainly among the Western players, the fine chemical industry is still fragmented. The top ten companies have a combined market share of 25%. In comparison the top ten pharmaceutical companies have more than 40%. The top ten individually have sales of $(0.5–1.5) × 10⁹ per year (see Table 2.). Most are divisions of large, diversified chemical companies. Six are headquartered in Europe, and one each in China, India, Japan, and the USA. All are active both in standard products (especially API-for-Generics) and custom manufacturing. They have extensive resources in terms of specialists, plants, process knowledge, backwards integration, international presence, etc. The manufacturing plants spread over many different locations. Many have grown to their present size through massive acquisitions.

Table 2. Top ten fine chemical companies or units (Sources: Company Annual Reports 2011,∗ author's estimate)

The portfolios of the midsized companies also comprise both exclusive synthesis and API-for-Generics. Sales are in the range of $100–500 × 10⁶ per annum. They include both subsidiaries of major public companies and family owned independents. Examples of the latter are Bachem, Switzerland; Dishman, India; F.I.S. and SIMS, Italy; Hikal, India; and Hovione, Portugal. Most of the midsized fine chemical companies are located in Europe, particularly in France, Germany, Italy, the UK, and Switzerland. Italy and Spain, where international drug patent laws were not recognized until 1978 and 1992, respectively, are strongholds of API-for-Generics (see Section 6.1). Because of a lack of economy in size, the large fine chemical companies traditionally do not perform better than the midsized ones. As most fine chemicals are produced in quantities of not more than a few tens of tonnes per annum in multipurpose plants (see Section 5.1), the production trains are similar in size throughout the industry. Their main constituents, the reaction vessels, have a median size of 4–6 m³. Various products are made throughout a year in campaigns. Therefore, the unit cost per cubic meter per hour (see Section 5.2) hardly depends on the size of the company. Last but not least, the large fine chemical companies operate many small rather sites than one big one. An example in case is Lonza. The Custom Manufacturing division alone operates 11 sites worldwide.

Finally, there are hundreds of small independents with sales below $100 million per annum. Most of them are located in Asia. They have only limited capabilities and often specialize in niche technologies, such as reactions with hazardous gases (e.g., ammonia/amines, diazomethane, ethylene oxide, halogens, hydrogen cyanide, hydrogen sulfide, mercaptans, ozone, nitrous oxides, and phosgene).

The plants of big and medium-size fine chemical companies comply with current good manufacturing practice (cGMP) regulations governing the production of pharmaceutical fine chemicals (see Chap. 7). With the exception of biopharmaceuticals, which are manufactured by only a few, the technology toolboxes of all these companies are similar. This means that they can carry out most types of chemical reactions. They differ in the breadth and quality of the offered service.

The minimum economical size of a fine chemical company depends on the availability of infrastructure. If a company is located in an industrial park, where analytical services; utilities, safety, health, and environmental (SHE) services, and warehousing are readily available, there is practically no lower limit.

Several large pharmaceutical companies market fine chemicals by themselves as subsidiary activity to their production for captive use, e.g., Abbott, USA; Bayer Schering Pharma, Boehringer-Ingelheim, Germany; Daiichi-Sankyo (after the takeover of Ranbaxy), Japan; Johnson & Johnson, USA; and Merck KGaA, Germany; and Pfizer (formerly Upjohn), USA.

Whereas the pharmaceutical industry is the dominant customer base for most fine chemical companies, some have a significant share of products and services for the agrochemical industry. Examples are Archimica, Saltigo (both Germany), DSM (The Netherlands), Pyosa (Mexico), and Hikal, India.

2.3. Contract Research Organizations

Contract research organizations (CROs) concentrate on research and process development, providing laboratory-scale process development and bench-scale synthesis services to the specialty chemical industry along product development. There are more than 2000 CROs operating worldwide, representing revenues of more than $20 × 10⁹. One distinguishes between patient CROs and product CROs.

Product CROs, a.k.a. chemical CROs, provide primarily process research and development services. An overlap with CMOs exists with regard to pilot plants (100 kg quantities), which are part of the arsenal of both CMOs and product CROs. Their tasks are described in Table 3. Companies offering both contract research and manufacturing services (CRAMS), a.k.a. one-stop shops, also exist.

Table 3. Tasks of product contract research organizations*

The offerings of patient CROs, a.k.a. clinical CROs, comprise more than 30 tasks addressing the clinical part of pharmaceutical development at the interface between drugs, physicians, hospitals, and patients. Only in a few cases (e.g., Aptuit, Cardinal Health, and Charles River Laboratories) do they also provide chemical R&D services.

There are about 50–100 product CROs in developed countries, either standalone companies or divisions of larger chemical companies, with a widely differing degree of width and depth of their offerings. Major customers for CRO services are the large global pharmaceutical companies. Half a dozen Big Pharmas (Pfizer, GlaxoSmithKline, Sanofi-Aventis, AstraZeneca, Johnson & Johnson, and Merck) alone absorb about one-third of all CRO spending. As for CMOs and also for CROs, biotech start-up companies with their dichotomy between ambitious drug development programs and limited resources are the second most promising prospects after Big Pharma. Contrary to manufacturing companies, the currency of CROs is not the unit product price, but full-time equivalents (FTEs), that is, the cost of a scientist working one year on a given customer assignment. Asian, especially Chinese and Indian, companies are emerging as low-cost contract research providers. The largest Chinese chemical CRO is WuXi AppTec, Shanghai WaiGaoQiao Free Trade Zone. Set up in the year 2001 and led by 50 returnees. 4500 employees generated sales of $334 × 10⁶ in 2011.

Contract research and manufacturing organizations (CRAMs) are hybrids combining the activities of CROs and CMOs [4]. Their history is either a forward integration of a CRO, which adds industrial-scale capabilities (an early example is Suven, India; recent ones are AMRI Global and Cambridge Major in the USA), or backwards integration of a CMO. It is questionable, though, whether one-stop shops really fulfill a need. The pros and cons are summarized in Table 4.

Table 4. Pros and cons of the one-stop-shop concept.

The first pro entry in Table 4., chance to establish... is particularly noteworthy. Most new drugs fail in early-stage development. The situation has worsened over the years. Nowadays, even for developmental drugs in phase II, the probability of reaching the market is less than 10%. Furthermore, as there is little repeat business, and as in Big Pharma different functions are in charge of placing orders, CRO projects only rarely evolve to industrial-scale supplies. Actually, the large fine chemical companies consider the preparation of samples more as a marketing tool (and expense) rather than a profit contributor.

2.4. Laboratory Chemical Suppliers

Before the life sciences industry, colleges and universities, medical research institutions, hospital research labs, government agencies, and other facilities can initiate any chemical research activity they need chemicals (a.k.a. reagents), solvents, and laboratory equipment. The laboratory chemical suppliers offer a large number (tens of thousands) of fine chemicals in small quantities for research purposes. Their combined revenues are about $10 × 10⁹. Major companies or business units are listed in Table 5. Online ordering is possible from all these companies.

Table 5. Laboratory chemical suppliers.

Apart from the top five, there are many laboratory chemical suppliers with smaller catalogues geared to specific needs, such as Honeywell Riedel-de-Haën for inorganic chemicals, BioCatalytics, which offers a ketoreductase kit with about 100 enzymes, or Chiral Technologies, a division of Daicel, Japan, which offers a range of 175 immobilized and coated polysaccharide chiral stationary phases for use with high-pressure liquid chromatography (HPLC), supercritical fluid (SCF), and simulated moving-bed (SMB) equipment. A selection of N-heterocyclic compounds, especially azaindoles, naphthyridines, pyridines, and pyrrolidines, is offered by Adesis, USA. Peptide building blocks are offered by Bachem, Switzerland (9000 products).

3. Products

In terms of molecular structure, one distinguishes first between low molecular weight (LMW) and high molecular weight (HMW) products. The generally accepted threshold between LMW and HMW is a molecular weight of about 700. The LMW fine chemicals, also designated small molecules, are produced by traditional chemical synthesis, by white biotechnology (see Section 4.2.1), or by extraction from plants and animals. In the production of modern life sciences products, total synthesis from petrochemicals prevails. The HMW fine chemicals, a.k.a. big molecules, are obtained mainly by red biotechnology processes. Peptides and proteins are the most important product categories.

3.1. Small Molecules

Many natural or synthetic LMW fine chemicals contain heterocyclic moieties. Widely occurring natural products are chlorophyll, hemoglobin, nucleosides (e.g., uridine), and the vitamins biotin (H), folic acid, niacin (PP), pyridoxine HCl (B6), riboflavin (B2), and thiamine (B1).

In life sciences, eight out of the top ten small-molecule proprietary pharmaceuticals contain one or more heterocyclic moieties; six of them contain an N heterocycle, one an S heterocycle, and one both an N and an S heterocycle (see Table 12.). The same 8/10 share of molecules with a heterocyclic moiety is found within the top ten agrochemicals (see [[1], Table 11.7, p. 118]. Further examples of pharmaceuticals are the β-lactam and quinolone antibiotics, the benzodiazepine antidepressants and the -vir antivirals. Widely used heterocyclic agrochemicals are the dipyridyl and triazine herbicides, the neonicotinoid, pyrazole, and anthranilic diamide insecticides and triazole conazole and aminopyrimidine and benzimidazole fungicides.

Even modern pigments, such as diphenylpyrazolopyrazoles, quinacridones, and engineering plastics, such as polybenzimidazoles, polyimides, and triazine resins, exhibit an N-heterocyclic structure.

3.2. Big Molecules

Big molecules are mostly oligomers or polymers of small molecules or chains of amino acids. Thus, within pharmaceutical sciences, peptides, proteins, and oligonucleotides constitute the major categories.

Peptides and proteins are oligomers or polycondensates of amino acid residues linked together by a carboxamide group. The threshold between the two is as at about 50 amino acid residues. Because of their unique biological functions, a significant and growing part of new drug discovery and development is focused on this class of biomolecules.

For the synthesis of peptides, four categories of fine chemicals, commonly referred to as peptide building blocks (PBBs), are used. In order of increasing sophistication they are amino acids (= starting materials), protected amino acids, peptide fragments, and peptides themselves [5] (see also Section 4.1). Along the way, the molecular weights increase from about 10² up to 10⁴ and the unit prices from about $10⁰ up to $10⁵ per kilogram. However, only a small part of the total amino acid production is used for peptide synthesis. In fact, l-glutamic acid, d,l-methionine, l-aspartic acid, and l-phenylalanine are used in large quantities as food and feed additives. Nowadays, about 50 peptide drugs are commercialized. The number of amino acid residues that make up a specific peptide varies widely. At the low end are the dipeptides. The most important drugs with a dipeptide (l-alanyl-l-proline) moiety are the -pril cardiovascular drugs, such as enalapril, captopril, imidapril, and lysinopril. Also the artificial sweetener Aspartame (N-l-α-aspartyl-l-phenylanaline 1-methyl ester) is a dipeptide. At the high end there is the anticoagulant hirudin (MW ≈ 7000), which is composed of 65 amino acids.

The total production volume (excluding Aspartame) of chemically synthesized, pure peptides is about 1500 kg and sales approach $500 × 10⁶ on the API level and $10 × 10⁹ on the finished drug level. The numbers would be much higher, about 10% of total pharma sales, if also peptidomimetics and APIs which contain peptide sequences as part of a molecule were included, such as the above mentioned -prils or the first generation anti-AIDS drugs, the -navirs. The bulk of the production of peptide drugs is outsourced to a few specialized contract manufacturers, such as Bachem Switzerland; Chengu GT Biochem, China; Chinese Peptide Company, China; Lonza, Switzerland; and Polypeptide, Denmark.

Proteins are very high molecular weight (M > 100 000) fine chemicals consisting of amino acid sequences linked by peptide bonds. They are essential to the structure and function of all living cells and viruses and are among the most actively studied molecules in biochemistry. They can be made only by advanced biotechnological processes, primarily mammalian cell cultures (see Section 4.2.2). Monoclonal antibodies (mAb) prevail among human-made proteins. About a dozen of them are approved as pharmaceuticals, of which five rank among the top ten drugs (see Table 6.).

Table 6. Reactions used to synthesize selected APIs*

Oligonucleotides are a third category of big molecules. They are oligomers of nucleotides, which in turn are composed of a five-carbon sugar (either ribose or desoxyribose), a nitrogenous base (a pyrimidine or a purine), and 1–3 phosphate groups. The best known representative of the nucleotides is the coenzyme adenosine triphosphate (ATP, M = 507.2). The maximum length of synthetic oligonucleotides hardly exceeds 200 nucleotide components.

Adenosine triphosphate

Peptides and oligonucleotides are now often summarized under the heading tides. They are used in a variety of pharmaceutical applications including antisense agents, which inhibit undesirable cellular protein production, antiviral agents, and protein binding agents. An antisense drug in advanced (phase III) development is Genzyme's cholesterol-lowering drug Kynamro (mipomersen).

Antibody–drug conjugates (ADC) are a combination between small and big molecules. The small-molecule parts, up to four different APIs, are highly potent cytotoxic drugs. They are linked with a monoclonal antibody, a big molecule which is of little or no therapeutic value in itself but extremely discriminating for its targets, the cancer cells. The first commercialized ADCs were Isis's Formivirisen and, more recently, Pfizer's (formerly Wyeth) Mylotarg (gemtuzumab, ozogamicin), a conjugate of N-acetyl-γ-calicheamicin with the humanized mouse monoclonal IgG4 κ antibody hP67.6.

4. Technologies

Several key technologies are used for the production of fine chemicals, including

Chemical synthesis, either from petrochemical starting materials or from extracts from natural products.

Biological sources—there are an estimate of 10–100 million different life forms on earth—are still only scarcely investigated. For instance, out of an estimated number of 1.5 million fungi, only 70 000 are known; and out of an estimated 0.4–3 million bacteria, only 6000 are known

Biotechnology, in particular biocatalysis (enzymatic methods), fermentation, and cell culture technologies.

Extraction from animal tissues, microorganisms, or plants; isolation and purification, used, for example, for alkaloids, antibacterials (especially penicillins), and steroids.

Hydrolysis of proteins, especially when combined with ion-exchange chromatography, used, for instance, for amino acids.

Chemical synthesis and biotechnology are most frequently used, sometimes also in combination.

4.1. Traditional Chemical Synthesis

Examples of the reactions used to synthesize a number of well-known pharmaceuticals are shown in Table 6. The number of synthetic steps required to make the desired APIs ranges from two (acetaminophen) to seven (omeprazole).

For each step of a synthesis, a large toolbox of chemistries is available. Most of them have been developed on laboratory scale by academia over the last century and subsequently adapted to industrial scale. For example, evaporating to dryness had to be elaborated to concentrate in a thin-film evaporator and precipitate by addition of propan-2-ol. The two most comprehensive handbooks describing organic synthetic methods in general are the Encyclopedia of Reagents for Organic Synthesis [6] and Houben-Weyl, Methods of Organic Chemistry [7]. For the synthesis of pharmaceutical fine chemicals (PFCs), consult Pharmaceutical Substances [8].

More than 150 types of reaction offered by the fine chemical industry are listed in the process directory Section of the Informex Show Guide [9]; 45 of them are organic name reactions, representing 10% of a more extensive listing in the Merck Index [10]. They range from acetoacetylation to Wittig reactions. Each of the 430 companies participating at the survey indicated competence for close to 30 types of reaction on average. Amination, condensation, esterification, Friedel–Crafts, Grignard, halogenation (especially chlorination), and hydrogenation and reduction (both catalytic and chemical) are most frequently mentioned. Optically active cyanohydrin, cyclopolymerization, ionic liquids, nitrones, oligonucleotides, peptide (both liquid- and solid-phase), electrochemical reactions (e.g., perfluorination), and steroid synthesis are promoted by only a limited number of companies.

The commercial importance of single-enantiomer fine chemicals has increased steadily since the mid-1990s. They constitute about half of both existing and developmental drug APIs. In this context, the ability to synthesize chiral molecules has become important. Two types of basic processes are available, namely, traditional physical separation of the enantiomers and stereospecific synthesis using chiral catalysts. Among the latter, enzymes and synthetic BINAP types are used most frequently. Large volume (> 10³ × 10⁶ t/a) processes using chiral catalysts include the manufacture of the perfume ingredient l-menthol as well as Syngenta's Dual (metolachlor) and BASF's Outlook (dimethenamid-P) herbicides. Examples of originator drugs which apply asymmetric technology are AstraZeneca's Nexium (esomeprazole), which uses chiral oxidation, and Merck's Januvia (sitagliptin), for which asymmetric hydrogenation of an unprotected enamine is carried out in the final steps of the synthesis.

The physical separation of chiral mixtures and purification of the desired enantiomer can be achieved by classical crystallization (having a low-tech image, but still widely adopted), making use of standard multipurpose equipment, or by various types of chromatographic separations, such as standard column, simulated moving bed (SMB), or supercritical fluid (SCF) techniques. The latter are advanced chromatographic technologies for the separation of demanding racemates and elimination of trace impurities.

Solid-phase peptide synthesis was pioneered by R. B. Merrifield in the early 1960s. Nowadays, the leading solid phases are the 2-chlorotrityl chloride resins. They consist of a polystyrene-base resin cross-linked with a small amount of divinylbenzene and functionalized with 2-chlorotrityl chloride.

With the exception of some stereospecific reactions, particularly biotechnology (see below), mastering these technologies does not represent a distinct competitive advantage. Most reactions can be carried out in standard multipurpose plants. The very versatile organometallic reactions (e.g., conversions with lithium aluminum hydride, boronic acids) may require temperatures as low as −100°C, which can be achieved only in special cryogenic reaction units, either by using liquefied nitrogen as coolant or by installing a low-temperature unit. Other reaction-specific equipment, such as ozone or phosgene generators, can be purchased in many different sizes. The installation of special equipment generally is not a critical path on the overall project for developing an industrial-scale process of a new molecular entity.

4.2. Biotechnology

Biotechnology is more and more used in the fine chemical industry for partial or total synthesis, either by conversion of renewable resources, such as sugar or vegetable oils, or the more efficient transformation of conventional raw materials. One distinguishes between white, red, and green biotechnology. As opposed to green and red biotechnology, which relate to agriculture and medicine, respectively, white, or industrial, biotechnology, enables the production of existing products in a more economic and sustainable fashion on the one hand, and provides access to new products, especially biopharmaceuticals on the other. Three different process technologies—biocatalysis, biosynthesis (microbial fermentation), and cell cultures—are used.

4.2.1. White Biotechnology

Biocatalysis, also termed biotransformation and bioconversion, makes use of natural or modified isolated enzymes, enzyme extracts, or whole-cell systems for enhancing the production of small molecules [11]. The syntheses are shorter, less energy intensive, generate less waste, and hence are both environmentally and economically more attractive than conventional methods. It requires only mild reaction conditions (ambient temperature and pressure at physiological pH) and affords high chemo-, regio-, and stereoselectivities. Furthermore, it generally needs fewer steps, e.g., by eliminating the need for protection and deprotection steps (see Figs. 2 and 3) and avoids the use of environmentally unattractive organic solvents. A starting material is converted by the biocatalyst to the desired product. Enzymes are differentiated from chemical catalysts particularly with regard to stereoselectivity, regioselectivity, and chemoselectivity. Whereas they were traditionally associated with the metabolic pathway of natural substances, they can also be tailored for use in chemical synthesis. Biocatalysts are applied like chemical catalysts, either in solution or on solid supports. Immobilized enzymes can be recovered by filtration after completion of the reaction. Conventional plant equipment can be used with minor adaptations.

Figure 2. Chemical versus enzymatic synthesis of Crestor (rosuvastatin)4-Cl-AA-OEt = Ethyl 4-chloro acetoacetate

Figure 3. Chemical versus enzymatic synthesis of Dilthiazem

The International Union of Biochemistry and Molecular Biology (IUBMB) has developed a classification for enzymes. The main categories are oxidoreductases, used inter alia in the synthesis of chiral molecules; transferases, which transfer a functional group, e.g., CH3 or OPO3; hydrolases, used inter alia to catalyze the C≡N → CONH2 reaction for the synthesis of acrylamide from acrylonitrile or nicotinic acid from 3-pyridylnitrile; and lyases, isomerases, and ligases, which bond two molecules with covalent bonds.

Whereas in the past, only about 150 out of 3000 known enzymes were used commercially, new developments in technology are increasing this number dramatically. Both natural diversity and synthetic reshuffling are being exploited to obtain enzymes with a large variation in properties. Companies specializing in making enzymes, such as Novozymes and Danisco (Genencor), or modifying (tailoring) them to specific chemical reactions, such as Codexis, have yielded enormous progress regarding areas of application, specificity, concentration, throughput, stability, ease of use, and economics. Nonetheless, the commercialization of many enzymatic processes is hampered by the lack of operational stability, coupled with their relatively high price.

In the manufacture of fine chemicals, enzymes are the single most important technology for radical cost reductions. This is particularly the case in the synthesis of molecules with chiral centers. Here, it is possible to substitute the formation of a salt with a chiral compound, e.g., (+)-α-phenylethylamine, crystallization, salt breaking, and recycling of the chiral auxiliary, resulting in a theoretical yield of not more than 50%, with a one-step, high-yield reaction resulting in a product with a very high enantiomeric excess. Two prime examples are AstraZeneca's blockbuster drug Crestor (rosuvastatin, see Fig. 2) and the widely used generic dilthiazem (see Fig. 3).

The two main advantages of the process, which was developed by DSM, are operational simplification (much smaller plant, ten times higher throughput) and cost savings on raw materials, mainly 2-aminothiophenol, which is used in a later stage in the process. The resulting cost reduction of the API is 40%.

Further examples of blockbuster drugs for which enzymes are used in the synthesis, are Pfizer's Lipitor (atorvastatin), for which the pivotal intermediate (R)-3-hydroxy-4-cyanobutyrate is now made with a nitrilase, and Merck's Zocor (simvastatin) and Singulair (montelukast), for which the reduction of a ketone to an S alcohol, which required stoichiometric amounts of expensive and moisture-sensitive (–)-DIP chloride has now been replaced by a ketoreductase enzyme catalyst step.

Similar rewarding switches from chemical steps to enzymatic ones have also been achieved in steroid synthesis. Thus, it has been possible to reduce the number of steps required for the synthesis of dexamethasone from bile from 28 to 15, and further reductions are in the making.

Biosynthesis by microbial fermentation, i.e., the conversion of organic materials to fine chemicals by microorganisms, has been used for 10 000 years to produce food products, like alcoholic beverages, cheese, yogurt, and vinegar. Nowadays, it is applied for the production of both small molecules (using enzymes in whole cell systems) and less complex, nonglycosylated big molecules, including peptides and simpler proteins. In contrast to biocatalysis, a biosynthetic process does not depend on chemicals as starting materials, but only on cheap natural feedstocks such as glucose to serve as nutrient for the cells. The enzyme systems triggered in the particular microorganism strain lead to the excretion of desired product into the medium or, in the case of HMW peptides and proteins, to the accumulation within inclusion bodies in the cells. The key elements of fermentation development are strain selection and optimization, media, and process development. For the large-scale industrial production of fine chemicals and proteins, dedicated plants are used. As the volume productivity is low, the bioreactors, called fermenters, need to be large. Their volumes can exceed 250 m³. Product isolation was previously based on large-volume extraction of the medium containing the product. Modern isolation and membrane technologies, like reverse osmosis, ultra- and nanofiltration, or affinity chromatographic methods, can help to remove salts and byproducts and to concentrate the solution efficiently and in an environmentally friendly manner under mild conditions. Final purification is often achieved by conventional chemical crystallization processes.

In contrast to the isolation of small molecules, the isolation and purification of microbial proteins is tedious and often involves a number of expensive large-scale chromatographic operations.

Examples of large-volume LMW products made by modern industrial microbial biosynthetic processes are monosodium glutamate (MSG), vitamin B2 (riboflavin), and vitamin C (ascorbic acid). Since the discovery of penicillin by Fleming in 1928 many more antibiotics and other secondary metabolites have been isolated and manufactured by microbial fermentation on a large scale. Important ones besides penicillin are cephalosporins, azythromycin, bacitracin, gentamycin, rifamycin, streptomycin, tetracycline, and vancomycin.

More recently, GlaxoSmithKline patented an efficient fermentation route for the biosynthetic production of thymidine (thymine-2-desoxyriboside). Key to the invention is a recombinant strain that efficiently produces high titers of thymidine by blocking some enzymes in the thymidine regulating pathway. This microbial process has now replaced the chemical route and has enabled GSK to supply the anti-AIDS drug AZT (zidovudine) to third-world countries at low cost.

4.2.2. Red Biotechnology

Mammalian cell culture, also known as recombinant DNA technology, serves for producing big-molecule fine chemicals, including glycoproteins and monoclonal antibodies [12]. The first products made were interferon (discovered in 1957), insulin, and somatropin. The need for cell culture technology stems mainly from the fact that bacteria do not have the ability to perform many of the post-translational modifications that most large proteins require for in vivo biological activity. For mammalian cell culture, specific cell lines are developed. They are uniform cell populations that can be cultured continuously. Commonly used cell lines are Chinese hamster ovary (CHO) cells or plant cell cultures (see below).

Mammalian cell culture is a much more sophisticated and demanding technology than traditional organic synthesis (see Table 7., [13]). Since mammalian cells are heat- and shear-sensitive, the bioreactor batch requires more stringent control of operating parameters. In addition, the very low growth rate of mammalian cells results in cycle times ranging from 10 d to several months, as opposed to several days for white biotechnology. Production volumes are tens of kilograms as opposed to hundreds of tonnes. The low productivity of the animal culture makes it very vulnerable to contamination, because a small number of bacteria would soon outgrow a larger population of animal cells.

Table 7. Characteristics of mammalian cell culture and synthetic chemical technologies (all figures are illustrative only) [13]

Typical production volumes for biopharmaceuticals made by mammalian cell technology are EPO-alpha, 7 kg (worldwide); Etanercept, 463 kg (USA), Rituximab, 418 kg (USA); and Adalimumab, 61 kg (USA).

As the resulting manufacturing costs are higher by a factor of 10⁵ ($10⁶/kg vs. $10/kg), mammalian cell technology is only used when strictly indispensable.

Given the fundamental differences between the two process technologies, plants for mammalian cell culture technologies have to be built ex novo. The production of biopharmaceuticals starts by cultivating the cells, followed by inoculating a nutrient solution with cells from a cell bank. The latter are allowed to reproduce in stages on a scale of up to several thousand liters. The cells secrete the desired product, which is then isolated from the solution, purified, and formulated. Because of the sensitive nature of most biopharmaceuticals, their dosage forms are limited to injectable solutions, which must be kept at low temperature. Biopharmaceuticals are therefore strictly made to order. A process flow sheet for protein production from mammalian cells is shown in Figure 4.

Figure 4. 5000 L process for protein production from mammalian cells

Leading producers are Boehringer-Ingelheim's biopharmaceuticals division, Lonza, and Piramal Healthcare (formerly Avecia). The inherent intricacies of mammalian cell technology led several companies opt out or to substantially reduce their stake. Examples of fine chemical companies are Cambrex and Dowpharma in the USA; Avecia, DSM, and Siegfried in Europe; and WuXi Pharma Tec in China.

Plant cell culture is gaining ground as alternative technology. Plants produce a wide range of secondary metabolites, some of which have been found to be pharmacologically active. However, these compounds are generally produced in very small amounts over a long period of time, making commercially viable extraction difficult. The technology shows promise for the selective synthesis of chiral compounds with a polycyclic structure, as found in many cytostatics, such as camptothecine, vinblastine, and paclitaxel. The new process for the last-named, introduced by Bristol Myers Squibb in 2002, is a brilliant example of the industrial-scale application of plant cell fermentation. It starts with clusters of paclitaxel-producing cells from the needles of the Chinese yew, T. chinensis, and was introduced in 2002. The API is isolated from the fermentation broth and purified by chromatography and crystallization. The chemical process to paclitaxel includes 11 synthetic steps, starting from 10-deacetylbaccatin (III) and has a modest yield. A plant cell process is also in the making for insulin, demand for which is expected to reach 12 000 kg by 2012. The Canadian firm SemioSys Genetics, which is developing the process based on safflower, anticipates capital costs of 70% and product costs of 40% as compared to exiting insulin production relying on genetically engineered yeast (Saccaromyces cerevisiae) or Escherichia coli. Elelyso (taliglucerase alfa) from Protalix, Israel is the first approved drug made by plant expression technology. It is derived from a proprietary plant cell based expression platform using genetically engineered carrot cells.

The Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH—DSMZ (German Collection of Microorganisms and Cell Cultures) is the most comprehensive biological resource center in Europe. The nonprofit organization counts more than 18 000 microorganisms, 1200 plant viruses, 600 human and animal cell lines, 770 plant cell cultures, and more than 7100 cultures deposited for the purpose of patenting.

In conclusion, biocatalysis should be, or become, part of the technology toolbox of any fine chemical company. Cell culture fermentation, on the other hand, should be considered only by large fine chemical companies with a full war chest and a long-term strategic orientation.

5. Production

5.1. Plant Design

Fine chemical plants are either located on a separate industrial site or are part of a larger chemical complex. Only the production building is fine chemical specific (see Fig. 5). As fine chemicals are produced in limited quantities per definition, the multipurpose (MP) plant is the prevailing basic configuration. An overview can be found in [14]. It must be capable of handling a series of unit operations and performing many types of chemical reactions. It typically consists of three distinct sections: a reaction part, also referred to as wet section (Fig. 6); a product finishing part, also referred to as dry section, and an administrative part, comprising quality control laboratories, offices, maintenance, changing rooms, and other services. The main pieces of equipment used are agitated, jacketed vessels for carrying out the reaction, filters or centrifuges for solid/liquid separation, and dryers. In the same plant up to 20 or more different process steps can be executed per year.

Figure 5. Fine chemical complex Source: Lonza, Visp, Switzerland, © Lonza Ltd., Basel, Switzerland

Figure 6. Pharmaceutical fine chemical plant, wet section

As the requirement for single fine chemicals rarely exceeds 100 t/a (see Fig. 7), and because the majority of fine chemicals can be produced in standardized equipment, it does not make sense to build dedicated production units for individual products. Moreover, the product portfolio is regenerated at a fast pace, so that a specific product can be obsolete before the investment for a dedicated plant is recovered.

Figure 7. Production volumes of APIs for prescription drugs (sample: top 500 drugs)

In commercial plants the volume of the reactors, which determine the production capacity, ranges typically between 4 and 6 m³ (sometimes between 1 and 10 m³, or even more). As the annual capacity for a one-step synthesis process averages approximately 15–30 t of product per 1 m³ of reactor volume, a production bay equipped with 4 and 6 m³ reaction vessels is suitable for the production of around 100 t of a step per year. As illustrated in Figure 4., this corresponds to a typical production volume of an API. Whereas one-third of the top 500 drugs are produced in the volume range of 10–100 t/a, the requirement of 7% of the APIs exceeds 1000 t/a.

Standard reaction conditions and standard construction materials in multipurpose plants are usually:

These properties are adequate for the vast majority of production processes. To make a multipurpose plant more versatile, special features are available. Flexibility, however, always has its price. Highly specialized equipment should only be installed if there is a specific requirement. Excessive flexibility is counterproductive. In industrial practice, it has proved to be a good solution to provide space for special equipment in the basic design and to order and install it only in case of a real demand.

Examples of special equipment for the wet section of the plant are low-temperature or cryogenic reactors, allowing for temperatures as low as −100°C, high-temperature reactors (up to +300°C), high-pressure reactors, fractional rectification columns, thin-film evaporators, liquid–liquid extractors, and various types of chromatographic columns. In addition to traditional stainless steel and glass lining, more exotic materials of construction such as Hastelloy, tantalum, zirconium, and Inconel alloys are used.

In the dry section of the building, micronization equipment, conventional dryers, nutsche–dryer combinations, spray dryers, air classifiers, sieving equipment, packaging/labeling machines, and other equipment can be considered.

Another option is to create semi-specific production bays, For example, for hydrogenations, phosgenizations, Friedel–Crafts alkylations, and Grignard reactions.

The choice of the proper piping concept is essential for a valid multipurpose plant design. The basic requirements for a piping system are, beside corrosion resistance against a wide array of substances, ease of cleanability (due to quality and costs), and a high degree of flexibility to ensure the required multipurpose character of the plant.

The complexity of the plant design, the degree of sophistication, and the quality requirements of the fine chemicals to be produced; the necessity to process hazardous chemicals; the sensitivity of product specifications to changes of reaction parameters; and the availability of a skilled workforce all determine the degree of automation that is advisable. Full process control computerization for a multipurpose plant is much more complex than for a dedicated single-product plant and therefore will be also be much more expensive. The fact that automation systems need to be validated has become a critical aspect of all automation systems that are being applied for cGMP productions.

Fine chemical plants have only evolved in few aspects and discrete steps such as containment, automatic process control, and waste pretreatment over the past 25 years [15]. Different initiatives for radical improvements are under way. With modular multipurpose plants an efficient combination of the flexibility of batch plants with the high performance and easier scale-up of continuous flow chemistry is sought. For the PFC industry the European Roadmap for Process Intensification has formulated efficiency targets for an overall cost reduction of 20% in 5–10 years and 50% in 10–15 years [16].

Along the same lines, the FDA has started an initiative towards knowledge-based processing called Quality by Design It is summarized in a report [17]. Radically new concepts are described hereafter:

F³ Factory [18], i.e., flexible, fast, and future factory, is an ambitious private–public project aimed at developing the chemical plant of the future. The plant incorporates advances in process intensification concepts and modular plug-and-play chemical production technology. It is intended to be more economic, eco-efficient, and sustainable than conventional processes, both in continuously operating large-scale plants and in small and medium-sized batch plants. To demonstrate the technical feasibility, a modular continuous plant is being built at Chempark Leverkusen, Germany).

Microreactors or microreactor technology (MRT), as a part of process intensification, is being developed at several universities, e.g., ETHZ, Switzerland; MIT, USA; and MCPT, Japan, as well as leading fine chemical companies. The main advantages of microreactors are (1) much better heat and mass transfer, allowing energetic reactions to be carried out safely and rapidly with higher yields, selectivities, and product quality. (2) Processes do not need cumbersome scale-up from laboratory to pilot plant to industrial-scale plant [19]. Capacity increases are achieved both by scale-out of module volume and numbering up, i.e., using more units in parallel. Disadvantages are the high investment cost, problems