The acylated isoflavone glycosides from subterranean clover and red clover

Formononetin and biochanin A 7-O-glucosides (1a and 2a) and their malonate hemi-ester derivatives (1b and 2b) have been isolated from red clover and from the Yarloop strain of subterranean clover. Structure (2b) is a correction of an earlier structural assignment to this compound. Small amounts of the derived methyl esters (1c and 2c) are also present in both clovers. Similar derivatives of genistein have been obtained from the Yarloop strain, although only the 7-O-glucoside (3a) has been isolated in pure form. Studies on red clover and on nine strains of subterranean clover have demonstrated in all cases that the acidic malonate esters account for the predominant proportion of the glycosides.