LAUSR

Lipase-catalysed enantioselective acetylation and deacetylation routes were investigated to prepare 1,5,6-trisubstituted 7-oxabicyclo[2.2.1]hept-2-ene skeleton in enantio-pure form. The racemic alcohol (6) used in acetylation reaction was accessed through Diels-Alder reaction of TBDMS-protected furfuryl alcohol with maleic anhydride, followed by reduction-benzylation-desilylation sequence. After systematic screening of lipases and solvents, Candida antarctica B on acrylic resin in pentane was identified as the best system that gave >98% ee towards the (+) acetate with 40% conversion, in 30 minutes. Absolute stereochemistry of this product was confirmed by X-ray diffraction analysis of its 3,5-dinitrobenzoate derivative (9). Enantioselective deacetylation of the racemic acetate of this starting material was then studied with the same set of lipases. After various optimization studies, Candida antarctica B in toluene as the solvent was found to be the most effective that gave 49% conversion with >99% ee towards the (+)-alcohol (8) at the end of 18 hours.