SYNTHESIS OF 2'-ACYLATED AND 2''-O-ACYLATED MALTOTRIOSIDES AS POTENTIAL FLUORESCENCE-QUENCHED SUBSTRATES FOR ALPHA-AMYLASE

Several 2'- and 2''-O-acylated maltotrioside derivatives have been pre pared as substrates for use in fluorescence-quenched assays of alpha-a mylase. These maltotriosides carry a quenching group [2-(4-hydroxy-3-n itrophenyl)ethyl] at the reducing end and a fluorescent donor (2-amino benzoyl) at either of the non-reducing D-glucose units. The quenching groups were introduced via silver triflate-promoted glycosylation, whi lst several methods were investigated for the selective introduction o f the fluorescent group. Attempted enzymic acylation of the maltotrios ides with subtilisin in neat dimethylformamide gave the 2'- and 2''-O- acylated derivatives as the major products. These were shown to be the products of chemical rather than enzymic acylation, in contrast to th e analogous literature reaction with maltotriose. Intramolecular quenc hing of the compounds was demonstrated by measuring the increase in fl uorescence upon hydrolysis.