Regioselective acylation of disaccharides in tert-butyl alcohol catalyzed by Candida antarctica lipase

The acylation of several disaccharides by ethyl butanoate and ethyl dodecanoate was catalyzed by Candida antarctica lipase in tert-butyl alcohol, at temperatures ranging from 40 degrees to 82 degrees C (reflux temperature). The relative reaction rates of the various disaccharides were directly related to their solubility. The primary products were the monoesters derived from acylation of the primary alcohol groups. At higher conversions diesters were formed, and the ratio of diester to monoester was markedly dependent on the structure of the disaccharide. Thus, reaction of maltose with ethyl dodecanoate in refluxing tert-butyl alcohol afforded the 6'-monododecanoate even at high conversions. Trehalose, in contrast, afforded the 6,6'-diester. Acylation of the less soluble sucrose and lactose was much slower, but a moderate (37%) conversion of sucrose was observed after a prolonged reaction time (7 days). A number of other lipases and proteases were tested but C. antarctica lipase was unique in catalyzing the acylation of sucrose in refluxing tert-butyl alcohol. (c) 1996 John Wiley & Sons, Inc.