Synthesis of enantiomerically pure 7- and 8-hydroxystearic acids1 (7- and 8-HSA) has
been accomplished starting from chiral non racemic 1-pentadecen-4-ol 1a and 1-
tetradecen-4-ol 1b respectively, in accordance with the retrosynthetic procedure
depicted in the Scheme. Access to enantiomerically pure homoallylic alcohols 1a,b was
possible via kinetic resolution of the corresponding racemic acetates, catalyzed by
Novozym 435 (Lipase B from Candida antarctica).
Yamaguchi esterification2 of 1a,b with 4-pentenoic and 5-hexenoic acids 2a,b
respectively afforded the suitable dienic esters 3a,b which were submitted to Ring-
Closing Metathesis Reaction (RCM).3 Hydrogenation of the resulting complex reaction
mixtures followed by hydrolysis under basic conditions afforded the expected chiral non
racemic 7- and 8-HSA in about 40% total yield.
Scheme
