Design chemical transformations, accessibility

Increasing interest has been directed to the microbial synthesis of chiral compounds that would not be readily accessible by chemical synthesis, and a few examples are given to illustrate the diversity of reactions that have been examined the stereoselective hydrolysis of nitriles to carboxylic acids has already been noted. Both by microbiological reactions and by combinations of microbiological transformation of aromatic compounds followed by designed chemical transformation (see Chapter 4, Section 4.2.3) have been used. Illustrations of both will be given. 

Traceless linkers enable the solid-phase synthesis of products which were formerly only accessible by tedious, multistep solution-phase chemistry. Some of these linkers tolerate a broad range of reaction conditions, giving the chemist plenty of freedom in the design of new solid-phase synthetic sequences. Interestingly, polystyrene-bound selenium reagents can also mediate useful chemical transformations of substrates during their attachment to the support, and thereby function both as reagents and as linkers. 

The direct question the practical mouse asks is, Who shall bell the cat and this is clearly central to reducing any molecular design to practice. The accessibility of chemical transformations continues to expand, and any siunmary of the state of the art quickly becomes stale. But in addition to marshaling the ever-increasing powers of organic synthesis, flow chemistry, parallel synthesis techniques, and so on, there are additional considerations within the make component of the DMTA cycle in lead generation. 

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