A nuclear magnetic resonance spectroscopic and conformational study of eight pseudo-trehaloses (D-glucopyranosyl 5a-carba-D- and -L-glucopyranosides).

N.m.r. data (1H and 13C) are presented for eight pseudo-trehalose derivatives in which the D-glucopyranosyl moiety is alpha or beta and the 5a-carbaglucopyranoside moiety is alpha-D, beta-D, alpha-L, or beta-L. The differences in the chemical shifts and then n.O.e. effects have been correlated with the preferred conformations estimated from empirical force-field calculations (HSEA), which have been used to calculate the average parameters over the whole energy surface. Of the four alpha-D-glucopyranosyl derivatives, only that with a 5a-carba-beta-D-glucopyranoside moiety (3) was a substrate for glucoamylase.