Lipase catalyzed enantioselective desymmetrization of a prochiral pentane-1,3,5-triol derivative

The enantioselective desymmetrization of the prochiral 3-O-silyl protected pentanetriol derivative 3 was carefully investigated. At −10 °C, the bacterial lipase from Burkholderia cepacia immobilized on ceramic particles led to monoacetate (S)-4 in 52% yield and >99.9% ee. At a reaction temperature of −40 °C the yield and enantioselectivity were even higher, but the reaction time was very long. Theoretical simulations of the reaction progress indicated an enantioselectivity of 25:1 at −10 °C and 35:1 at −40 °C. (S)-4 was converted into the enantiomerically pure building block 5-azidopentane-1,3-diol (S)-7 in two steps. The absolute configuration of (S)-7 was determined by exciton-coupled circular dichroism (ECCD) of diester (S)-8.

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