Enzymatic synthesis of 2-chloro-4-nitrophenyl 4,6-O-3-ketobutylidene beta-maltopentaoside, a substrate for alpha-amylase.

A transglycosylation reaction with 2-chloro-4-nitrophenyl beta-maltoside as an acceptor was done with 4,6-O-3-ketobutylidene maltopentaose and Bacillus macerans cyclodextrin glucanotransferase in an aqueous solution containing 50% n-propanol, and there were two main transglycosylation products. They were identified as 2-chloro-4-nitrophenyl 4,6-O-3-ketobutylidene beta-maltopentaoside and 2-chloro-4-nitrophenyl 4,6-O-3-ketobutylidene beta-maltohexaoside, and their yields were 30% and 21% respectively on the basis of the decrease of 4,6-O-3-ketobutylidene maltopentaose. For the production of 2-chloro-4-nitrophenyl 4,6-O-3-ketobutylidene beta-maltopentaoside at high substrates concentrations, the addition of n-propanol in this reaction not only increased the solubility of 2-chloro-4-nitrophenyl beta-maltoside sufficiently but also suppressed side reactions.