Saponin and Sapogenol. XXX. Furostanol Glycosides from Metanarthecium luteo-viride MAXIM. : Bisdesmosides of Furometagenin and Furometanarthogenin

Abstract

Bisdesmosides of two new furostanols (named furometagenin and furometanarthogenin) were isolated as their 22-O-methylated peracetates (designated as NF-1 and NF-2) from the subterranean part of Metanarthecium luteo-viride MAXIM. (Liliaceae). The structures of NF-1 and NF-2 have been elucidated as 11-O-α-L-arabinopyranosyl-26-O-β-D-glucopyranosyl-22-O-methyl-furometagenin nonaacetate (12) and 11-O-α-L-arabinopyranosyl-26-O-β-D-glucopyranosyl-22-O-methyl-furometanarthogenin octaacetate (15) on the basis of chemical and physicochemical evidence. The 2β-acetoxy-4-en-3-one moiety included in the steroidal part of 15 has been demonstrated to undergo air oxidation during alkaline saponification followed by acidic hydrolysis in methanol and to give a new sapogenol : 2-methoxy-11α-hydroxy-25R-spirosta-1, 4-dien-3-one (2-O-methyl-dehydrometanarthogenin) (23). This secondary conversion in the A-ring of sapogenol part has been corroborated by the examination of the model steroids : 2β-and 2α-acetoxy-17β-chloroacetyl-androst-4-en-3-ones (25, 28).