Kinetic resolution of 1-biaryl- and 1-(pyridylphenyl)alkan-1-ols catalysed by the lipase B from Candida antarctica

Lipase B from Candida antaretica (CAL-B) catalyses the highly enantioselective (E > 200) transesterification of some 1-biaryl-2-yl-, -3-yl-, and -4-yl-ethanols and -propan-1-ols, as well as 1-(o-, m-, and p-pyridylphenyl)ethanols, 6, with vinyl acetate, Kazlauskas' rule being obeyed in all cases. meta and para-Substituted substrates were transformed within several hours (conversion degree ranging from 23-50%), reaction rates for propan-l-of derivatives being slower than those for ethanol derivatives. Transesterifications of ortho-substituted alcohols took several days and were accompanied by a chemoenzymatic side reaction: the formation of another acetate derived from the hemiacetal between 6 and acetaldehyde coming from vinyl acetate. This side reaction was suppressed in the presence of isopropenyl acetate as acyl donor, conversion degrees for transesterification ranging from 20-40% after ten days (E > 200). The usefulness of (R)-6p as ligand in the asymmetric addition of di-ethylzinc to benzaldehyde was also demonstrated.