Synthesis of calyxosides, two-headed glycosphingolipids isolated from marine sponges, and their α-glycoside analogs

Abstract

Calyxoside and calyxoside B are so-called “two-headed” glycosphingolipids isolated from marine sponges, and they exhibit cytotoxicity against HeLa cells. The synthesis of calyxoside and calyxoside B was achieved starting from Garner's aldehyde. The key β-glycosylation was performed using a sphingosine derivative, in which the amino groups were protected as azido groups, as the glycosyl acceptor. Unnatural α-glycosides, i.e., α-anomers of calyxoside and calyxoside B, were also synthesized by changing the glycosylation conditions. The cytotoxicity of natural calyxosides and their unnatural α-glycoside analogs against HeLa cells was evaluated.