Alkyl S-Glycosides As Electroactive Glycosyl Donors: Study of the Effect of the Steric and Electronic Properties of the Aglycone and Protective Groups over the Oxidation Potential

Abstract

The oxidation potentials (E ox) of a series of alkyl S-glycosides were determined using cyclic voltammetry and square-wave voltammetry. Model glycosides were designed to investigate the effect exerted by the steric and electronic properties of the alkyl aglycone and protective groups over the oxidation potentials. Glycosides substituted with small alkyl groups exhibited lower E ox while compounds with bulky substituents presented peaks at more positive potentials. The results show a good correlation of E ox with the volume of the aglycone substituent as well as with the calculated stability of the aglycone-derived thiyl radical. The effect of the protective groups on E ox is, as expected, predominantly electronic. However, the increase of the protective group bulkiness leads to more positive peak potentials suggesting a steric contribution to E ox modulation. The results of this study posse alkyl S-glycosides as convenient glycosyl donors for electrochemical glycosylations.