The Stereoselectivity of the α‐Alkylation of (+)‐(1R, 2S)‐cis‐Ethyl‐2‐hydroxy‐cyclohexanecarboxylateIn continuation of our work on the stereoselectivity of the α‐alkylation of β‐hydroxyesters [1] [2], we studied this reaction with the title compound (+)‐2. The latter was prepared through reduction of1with baker's yeast. Alkylation of the dianion of (+)‐2furnished (−)‐4in 72% chemical yield(Scheme 1)and with a stereoselectivity of 95%. Analogously, (−)‐7was prepared with similar yields. Oxidation of (−)‐4and (−)‐7respectively furnished the ketones (−)‐6(Scheme 3)and (−)‐8(Scheme 4)respectively, each with about 76% enantiomeric excess (NMR.). It is noteworthy that yeast reduction ofrac‐6(Scheme 3)is completely enantioselective with respect to substrate and product and gives optically pure (−)‐4in 10% yield, which was converted into optically pure (−)‐6(Scheme 3).The alkylation of the dianionic intermediate shows a higher stereoselectivity (95%) from the pseudoequatorial side than that of 1‐acetyl‐ or 1‐cyano‐4‐t‐butyl‐cyclohexane (71% and 85%) [9] or that of ethyl 2‐methyl‐cyclohexanecarboxylate (82%). The stereochemical outcome of the above alkylation is comparable with that found in open chain examples [1][2].Finally (+)‐(1R, 2S)‐2was also alkylated withWichterle'sreagent to give (−)‐(1S, 2S)‐9in 64% yield. The latter was transformed into (−)‐(S)‐10and further into (−)‐(S)‐11(Scheme 5). (−)‐(S)‐10and (−)‐(S)‐11showed an e.e. of 76–78% (see also [11]). Comparison