UTILIZATION OF TRITERPENOIDS .1. SYNTHESIS OF BETULIN GLYCOSIDES BY CYCLODEXTRIN GLYCOSYLTRANSFERASE

Some betulin glycosides were synthesized to utilize betulin as a biolo gically active compound and to clarify the correlation between the che mical structures, and the biological activities of triterpene glycosid es. Betulin-3-yl beta-D-cellobioside was synthesized by coupling 28-O- acetylbetulin with hepta-O-acetyl alpha-D-cellobiosyl bromide by means of a Koenigs-Knorr type condensation followed by deacetylation. Furth ermore, some betulin oligoglycosides with alpha-glycosidic linkages we re synthesized from alpha-cyclodextrin as a donor and betulin-3-yl bet a-D-cellobioside as an acceptor by the transglycosylation of cyclodext rin glycosyltransferase (CGTase) from Bacillus macerans. The addition of a small amount of surfactant made the enzymic reaction efficient. T he nuclear magnetic resonance (NMR) chemical shift assignments determi ned by a variety of two dimensional experiments resulted in the conclu sion that the main products of the enzymic reaction were betulin-3-yl beta -D-(4-O-beta-D-maltosyl)-glucoside and betulin-3-yl 8-D-(4-O-beta -D-maltotriosyl)-glucoside.