(R)-3-Hydroxy-3-methyl-5-hexanoic acid p-methoxybenzyl ester 1b was prepared by carbonchain elongation on both termini of the starting material, (R)-3-benzyloxy-2-methylpropane-1,2-diol 2a, which was prepared by an over-expressed Bacillus subtilis epoxide hydrolase-catalyzed enantioselective hydrolysis of the racemic 1-benzyloxymethyl-1-methyloxirane 3. One of the key steps of the requisite transformation was the Rhodococcus rhodochrous NBRC 15564-mediated hydrolysis of a cyano group to a carboxyl group under neutral conditions, to exclude any racemization of the intermediate and/or product. The enantiomerically pure form of (R)-1b was applied to a new formal total synthesis of taurospongin A.
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