Transesterification of lactulose with ethyl butanoate catalyzed by Candida antarctica lipase

The enzyme-catalyzed acylation of lactulose by ethyl butanoate was investigated. A slow conversion to a complex mixture of esters was observed at 40 °C in tert-butyl alcohol in the presence of a number of lipases and a protease. With Candida antarctica B lipase, esterifications could also be performed at 82 °C (reflux) to increase the rate. The reaction could be accelerated by a factor of 5 when 1,2-dimethoxyethane was used as solvent. In this way, a nearly quantitative conversion to a mixture of esters was accomplished within 24 h.