Enantioselective synthesis of the unsymmetrical bis(lactone) (-)-(3E,6R,9E,12S,14R)-colletol induced by chiral sulfoxides and an approach to (+)-colletodiol by asymmetric hydroxylation of an alpha,beta-hydroxy lactone

A general synthetic strategy towards the two bis(lactones) (-)-colletol (1) and (+)-colletodiol (2) is described. A common intermediate in this synthe sis is the 6-membered hydroxy lactone (+)-(3R,SR)-3-hydroxy-5-hexanolide (6 ), readily prepared by stereoselective reduction of (+)-(SR)-methyl 3,5-dio xo -6-(p-toluenesulfinyl)hexanoate (7). Stereoselective hydroxylation of th is hydroxy lactone has allowed efficient access to (+)-colletodiol(2).