A Study of the Calcium Complex of a Glucosylceramide, Soya-cerebroside II

In order to study calcium ion complex of soya-cerebroside II (1), an ionophoretic glucosylceramide isolated from soybean, C8-cerebroside (3) and 3, 3", 6"-trideoxy-C8-cerebroside (4) are designed and synthesized. On the basis of extensive ^1H-NMR studies in the presence of Ca^<2+> and a continuous variation method via ^1H-NMR, soya-cerebroside II is suggested to form a calcium complex with 1/Ca^<2+> ratio of 1:1. Soya-cerebroside II serves as a tridentate chelating ligand for Ca^<2+>; the amide carbonyl, C2'-hydroxy, and C2"-hydroxy oxygens are responsible for the Ca^<2+> binding. Soya-cerebroside II is structurally analogous to a neural glucosylceramide. Thus, the accumulated neural glucosylceramide inside of endoplasmic reticulum (ER) membrane may serve as an endogenous Ca^<2+>-binding and -transport molecule (ionophore) that result in mobilization of Ca^<2+> from intracellular calcium stores.