Preferred conformation of C-glycosides. 12. Synthesis and conformational analysis of α,α-, α,β-, and β,β-C-trehaloses

Article abstract of DOI:10.1021/jo00080a016

A single, unified strategy for the stereocontrolled synthesis of α,α-, α,β-, and β,β-C-trehaloses (1-3) was developed. The solution conformations of C-trehaloses 1-3, as well as their permethyl derivatives, were determined on the basis of vicinal coupling constants observed in the ¹H NMR spectra. The preferred conformations for α,α- and β,β-C- trehaloses (1 and 3), shown in Figure 1, were predicted and experimentally proven. A diamond-lattice analysis of α,β-C-trehalose (2), shown in Figure 2, revealed the relative stability of the three staggered conformers to be 2A > 2B > 2C, and the experimental data were found to be consistent with this trend. It was demonstrated that the inversion of the C.2 or C.2' hydroxyl group of 2 affected its conformational preference in a predictable manner. The ¹H NMR spectra of α,β-C-trehalose 2 provided direct experimental evidence to illustrate that the α-C-glycosidic bond is conformationally more rigid than the β-C-glycosidic bond.