A Bidirectional S(E)' Strategy for 1,5-syn and 1,5-anti Stereocontrol toward the Synthesis of Complex Polyols

Studies report a bidirectional S(E)' strategy applicable for the stereocontrolled synthesis of nonracemic 1,5-syn and 1,5-anti diols and their derivatives. Nonracemic 1,3,2-diazaborolidine auxiliaries are incorporated by chemoselective tin-boron exchange to provide reactive allylic boranes. The convergent pathway utilizes sequential reactions with two aldehydes producing stereochemical outcomes from cyclic, closed, and open transition state preferences, respectively. Synthesis of fragment 16 of peloruside A is accomplished in four steps from readily available aldehydes 9 and 13.