Optimization of lipase-catalyzed synthesis of (z)-3-hexen-1-yl acetate by direct esterification in hexane and a solvent-free medium

The lipase from Candida antarctica immobilized on an acrylic resin (Novozym 435) was investigated for its use in the synthesis of (z)-3-hexen-1-yl acetate by direct esterification in n-hexane and a solvent-free medium. A careful examination of major parameters (temperature, amount of lipase, substrates concentration, acid:alcohol ratio) established the suitability of Novozym 435 for the preparation of the title compound. Under the same conditions, the lipase from Mucor miehei immobilized on a microporous anion exchange resin (Lipozym IM) Sailed to produce acetate in appreciable yield. In n-hexane at 70 degrees C in the presence of 2% (w/w reactants) of the lipase nod 1.5 mol l(-1) of substrate, the ester yield reached 94% in less than 27 h; moreover, the lipase operated in the absence of solvent as well: 70% yield using 9% (w/w reactants) of lipase. This yield could be significantly improved (80-82%) by progressively adding a 50% excess of acetic acid to the mixture of Novozym 435 and (z)-3-hexen-1-ol. (C) 1995 Elsevier Science Inc.