Stereoselective phosphorylation of branched cyclodextrins with inorganic cyclo-triphosphate

The phosphorylation by inorganic sodium cyclo-triphosphate (P(3m)) having a six-membered ring was examined for cyclomaltohexaose (alpha-cyclodextrin) and branched cyclodextrins (mono-6-O-alpha-D-glucopyranosylcyclomaltohexaose, mono-6-O-alpha-D-maltosylcyclomaltohexaose, mono-6-O-alpha-D-glucopyranosylcyclomaltoheptaose, and mono-6-O-alpha-D-maltosylcyclomaltoheptaose) in aqueous solution. For all cyclomaltooligosaccharides (cyclodextrins) studied, the 2-OH group was stereoselectively phosphorylated. In the reaction of branched cyclodextrins and P(3m), only the 2-OH on the alpha-D-glucopyranosyl group of the cyclodextrin rings was phosphorylated with maximum yields of more than 27%. The phosphorylation mechanism of branched cyclodextrins with P(3m) is also discussed.