Iterative asymmetric synthesis of protected anti-1,3-polyols

A new general method for the iterative asymmetric synthesis of anti-1,3-pol yol chains has been developed. The alpha,alpha'-bisalkylation of 2,2-dimeth yl-1,3-dioxan-5-one SAMP-hydrazone 1 with benzyloxymethylchloride as the se cond electrophile leads to virtually diastereo- and enantiopure substituted 2,2-dimethyl-1,3-dioxan-5-ones with good overall yields. Their deoxygenati on and conversion into primary iodides affords the electrophile for the fur ther alkylation of 1. In this way the configurations of all new stereogenic centres are controlled by a single auxiliary. (C) 1999 Elsevier Science Lt d. All rights reserved.