Diasteromeric diols

Extension of DKR to polymer chemistry would readily result in chiral polyesters, polycarbonates, or polyamides from an optically inactive monomer mixture. Scheme 10 describes three variants of chemoenzymatic catalysis applied in polymer chemistry that recently appeared in the literature. Route A uses AA and BB monomers to prepare chiral polymers from racemic/diasteromeric diols. Route B converts an enantiomer mixture of AB monomers to homochiral polymers. Route C is the enzymatic ring-opening polymerization of co-methylated lactones to homochiral polyesters. Details will be given in Sect. 3.4.2. 

Fig. 15 Variants of the extension of DKR to polymercondensations Route A uses AA and BB monomers to prepare chiral polymers from racemi/diasteromeric diols. Route B converts an enantiomer mixture of AB monomers to homochiral polymers...

Vinyl Grignard reagent reacts with the aldehyde function in the open-chain form of compound 6. leading initially to diol 25 with a diastereoselectivity of 71 2 antr.syn). The diasteromeric alcohols atn be separated after silylation to 7, but this is unnecessary since both isomers lead to the same product in the subsequent reaction. 

The bulkiness and stereochemistry of large steroid substituents allows stereoselective hydrolyses of unnatural enantiomers. Cholesterol together with cholesterol esterase have been used to resolve binaphtols and other diols into their enantiomers the diasteromeric dicholesteryl-diesters are hydrolyzed selectively by the crude enzyme in two steps and the final diol is a pure enantiomer. 

---