Highly diastereo- and enantioselective synthesis of protected anti-1,3-diols

An efficient asymmetric synthesis of protected anti-1,3-diols 5 (de greater than or equal to 98%, ee = 92-98%) from 2,2-dimethyl-1,3-dioxan-5-one SAMP hydrazone 1 is described. The key steps are the diastereo- and enantiosele ctive alpha,alpha'-bisalkylation followed by reduction of the ketones 2 and a variant of the Barton-McCombie deoxygenation. The new method allows the synthesis of acetonide-protected anti-1,3-diols with a broad range of subst ituents in good overall yields (31-69%).