Regioselectivity in the formation of di- and tri-6-O-mesitylenesulfonates of α-cyclodextrin.

The quantitative analysis of the reaction products for α-cyclodextrin (α-CD) with mesitylenesulfonyl chloride (MessCl) showed that di- and tri-mesitylenesulfonylation of the primary hydroxy groups of α-CD is regioselective. The reaction of mono-6-O-mesitylenesulfonyl-α-CD with MessCl in pyridine gave less 6(A),6(C)-di-O-mesitylenesulfonyl-α-CD than 6(A),6(B)-di-O-mesitylenesulfonyl-α-CD. The reaction of 6(A),6(D)-di-O-mesitylenesulfonyl-α-CD with MessCl gave less 6(A),6(B),6(E)-tri-O-mesitylenesulfonyl-α-CD than 6(A),6(B),6(D)-tri-O-mesitylenesulfonyl-α-CD. These results indicate that the mesitylenesulfonyl group attached to glucopyranose-A (Glc-A) retards further mesitylenesulfonylation of the primary hydroxy group of Glc-C. The (1)H NMR spectra of these modified α-CDs showed that the signal for the primary hydroxy and anomeric protons of Glc-C are significantly shifted upfield by the mesitylenesulfonyl group of Glc-A.