Stereoselective Preparation of (1S, 2R)- and (1S, 2S)-2-Hydroxy-7, 7-dimethylbicyclo[2.2.1]heptane-1-carboxylic Acids

Starting with (1S)-ketopinic acid (7, 7-dimethyl-2-oxo-bicyclo[2.2.1]heptane-1-carboxylic acid), a facile high-yield synthesis of diastereomerically pure (1S, 2R)- and (1S, 2S)-2-hydroxy-7, 7-dimethylbicyclo[2.2.1]heptane-1-carboxylic acids, potentially useful as chiral auxiliaries, has been achieved : the key step for the latter (2-endo isomer) involves the base-catalyzed epimerization of the (1S, 2R)-2-hydoxy isomer (2-exo-isomer), exclusively formed by the L-Selectride[○!R] reduction of alkyl ketopinate, via the retro-aldol reaction.