Synthesis of enantioenriched alpha-(hydroxyalkyl)-tri-n-butylstannanes.

A catalytically asymmetric synthesis of α-(hydroxyalkyl)-tri--butylstannanes in good-excellent yields and enantioselectivities (up to 98% e.e.) via addition of ethyl(tri--butylstannyl)zinc to aldehydes was achieved. In practice, was isolated after protection as its more stable ester or thiocarbamate (PG). The reagent was prepared from equimolar amounts of tri--butylstannyl hydride and EtZn in DME so as to avoid contamination by lithium and magnesium ions which suppress enantioselectivity.