Hydrolytic enzymes in the synthesis of carba-sugars: application of the lipase from Pseudomonas fragi

Abstract

Pig liver esterase-catalysed hydrolysis of (±)-endo-2-methoxycarbonyl-7-oxabicyclo[2.2.1]hept-5-ene 1a provides (–)-endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylic acid 1b and (+)-endo-2-methoxycarbonyl-7-oxabicyclo[2.2.1]hept-5-ene 1a in 36 and 57% ee, respectively. Transesterification between (±)-2-exo-hydroxy-4,8-dioxatricyclo[4.2.1.0^3,7]nonan-5-one 2a and vinyl acetate catalysed by the lipase from Pseudomonas fragi gives the acetate (–)-2b and alcohol (+)-2a in 91 and 94% ee, respectively. Optically pure acetate (–)-2b is obtained after removal of contaminating racemate from the impure acetate by crystallisation of (–)-2b of 91% ee (EtOH).