The stereoselectivity of the alkylation of the dianion of ethyl 2‐hydroxy‐6‐methylcyclohexanecarboxylates: Control of stereochemistry at three adjacent stereogenic centers

Yeast reduction of rac‐ethyl 2‐methyl‐6‐oxocylohexanecarboxylate (rac‐1) yielded selectively (+)‐ethyl 2‐hydroxy‐6‐methylcyclohexane carboxylate (+)‐2 (Scheme 1) which has been alkylated with 5‐iodo‐2‐methylbut‐2‐ene by (the dianion method to furnish the 4‐methylbut‐3‐enyl derivat 3 (Scheme 3)). NaBH4 reduction of (+)‐1 led to three hydroxy‐carboxylates (−)‐2, (+)‐5, and (−)‐6 (Scheme 4). Allylation of the dianion of (+)‐5 afforded (+)‐7.