Two-Directional Desymmetrization by Double 1,4-Addition of Silicon and Boron Nucleophiles

The two-directional desymmetrization of prochiral precursors with alpha,beta-unsaturated branches by catalyst-controlled 1,4-addition of silicon and likewise boron nucleophiles allows for a general enantioselective access to syn,anti-triols with 1,n + 1,2n + 1 (n = 2 and 3) substitution patterns. The utility is demonstrated in the synthesis of the C17-C25 fragment of dermostatin A.