An efficient, regioselective and fast enzymatic glycosylation for cyclodextrins

The introduction of a short spacer arm was necessary to obtain complete regioselectivity in the glycosylation of β-cyclodextrin (β-CD) mediated by glycosidases. Thus 6-N-(2-aminoethyl-α-d-galactopyranosyl)-6-deoxycyclomaltoheptaose was prepared in four steps from β-cyclodextrin with 30% overall yield using, in the key step, the transfer activity of green coffee bean α-galactosidase.