Saponin and Sapogenol. XXVII. Revised Structures of Holotoxin A and Holotoxin B, Two Antifungal Oligoglycosides from the Sea Cucumber Stichopus japonicus SELENKA

Abstract

The chemical structures of two antifungal oligoglycosides holotoxin A and B, which were isolated from the sea cucumber Stichopus japonicus SELENKA, have been reinvestigated. On the basis of chemical and physicochemical evidence, the genuine sapogencl of holotoxin A and B has been elucidated to be holotoxigenol rather than previously proposed stichopogenin A₄ (3), and it has been shown that the structures of holotoxin A and B should be revised as 3-O-{2-O-[3-O-methyl-β-D-glucopyranosyl (1→3)-β-D-glucopyranosyl-(1→4)-β-D-quinovopyranosyl]-4-O-[3-O-methyl-β-D-glucopyranosyl (1→3)-β-D-glucopyranosyl]-β-D-xylopyranosyl}-holotoxigenol (6) and 3-O-{2-O-[3-O-methyl-β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl (1→4)-β-D-quinovopyranosyl]-4-O-[β-D-glucopyranosyl (1→3)-β-D-glucopyranosyl]-β-D-xylopyranosyl}-holotoxigenol (9), respectively.