Drug synthesis overview

In recent years, significant research effort has been directed toward identification of new methods for benzimidazole synthesis. Recent advances, particularly in transition metal-mediated reactions, have ushered in novel synthetic approaches for the construction and functionalization of this useful ring system. The present overview of new transition metal-mediated synthetic approaches focuses primarily on methodologies reported from 2008 to early 2012 that may soon find broader application in drug synthesis. 

Chiral separation of drng molecules and of their precursors, in the case of synthesis of enantiomerically pure drugs, is one of the important application areas of HPLC in pharmaceutical analysis. Besides HPLC, capillary electrophoresis (CE) is another technique of choice for chiral separations. Chapter 18 provides an overview of the different modes (e.g., direct and indirect ones) of obtaining a chiral separation in HPLC and CE. The direct approaches, i.e., those where the compound of interest is not derivatized prior to separation, are discussed in more detail since they are cnrrently the most frequently used techniques. These approaches require the use of the so-called chiral selectors to enable enantioselective recognition and enantiomeric separation. Many different molecnles have been nsed as chiral selectors, both in HPLC and CE. They can be classified into three different groups, based on their... 

No attempt will be made to give an overview of the main pathways of the several dozen neurotransmitters, neuromodulators and co-transmitters which are possibly involved in the aetiology of mental illness. Instead a summary is given of the relevant pathways involved in the synthesis and metabolism of those transmitters which have conventionally been considered to be involved in the major psychiatric and neurological diseases and through which the psychotropic drugs used in the treatment of such diseases are believed to operate. 

To give an overview of the breadth of applications of NMR, Fig. 12.1 summarizes the drug development process and indicates the role of NMR at various stages. Drug development is an iterative process and can be simplified by representing it with two interconnected cycles of activity. Cycle A involves the design or discovery of an initial lead followed by its synthesis and bioassay. Based on the initial assay results there may be several loops around this... 

This section is intended to give a short overview of method development and validation of analytical methods - for qualitative and quantitative analysis of small (Mw < 1000) drugs - from process liquid such as fermentation medium. The same principles can be applied for any low-molecular weight compounds in biotechnological or organic synthesis. 

Frequently, during organic synthesis or drug metabolism studies, unknown compounds are isolated and their structure must be confirmed or, if they are totally unknown, solved using a combination of analytical techniques. Exercises of this type use qualitative spectroscopy rather than the quantitative aspects discussed so far. Whole university courses and many textbooks and online tutorials have been produced to cover elucidation of chemical structure, and a detailed treatment of the subject is beyond the scope of this book. However, a brief overview of the major techniques and their limitations may be useful. 

Table 3 gives an overview of the microfluidic unit operations and applications that have been already implemented on the segmented flow platform. They all take advantage of the enclosed reaction confinement within the droplets, either for analytical applications (cell analysis, single organism analysis, DNA assays, drug screening, protein crystallization) or chemical synthesis. 

See also Drug Design, Salvage Routes to Deoxyribonucleotide Synthesis, DNA Replication Overview (from Chapter 24), Eukaryotic DNA Polymerases (from Chapter 24), Retrovirus Replication (from Chapter 24)... 

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