Regioselective enzymatic hydrolysis of hexa-O-acetyl-lactal in a green non-aqueous medium

A purified lipase fraction from Rhizomucor miehei (RML) was immobilized and used to selectively hydrolyze hexa-O-acetyl-lactal (1) to penta-O-acetyl-3-hydroxylactal (2). The reaction was performed in low-water content tert-butanol (7% USP water), thus allowing the control of by-product formation. This solvent was superior to the established buffer/acetonitrile system in terms of reagent/product solubility, biocatalyst stability and environmental impact. The reaction was scaled up till 28 g/L (50 mM) affording the product 2 in very high yield (85%) and purity (98%).