Lipase AKG mediated resolutions of α,α-disubstituted 1,2-diols in organic solvents; remarkably high regio- and enantio-selectivity

Diols 1, which contain adjacent tertiary and primary hydroxy groups, can be selectively mono-acylated at the primary hydroxy group by many lipases in organic solvents. Since the reaction does not take place at the chiral tertiary centre itself, observed enantioselectivities are usually low. Only the combination of one lipase, lipase AKG (Amano, Pseudomonas sp.), with selected substrates gives high enantioselectivities (E 20 to > 200). Also, the solvent and acyl donor employed influences the outcome. On the basis of the results of lipase AKG towards substrates 1 an active site model for this specific lipase has been developed, which can account for the results obtained. Full experimental details on the synthesis of diols 1 and enzymatic preparation of acetates 2 are given. Also, the absolute stereochemistry of the enzymatically prepared diols 1 has been established by independent synthesis from (R)-mandelic acid.