New 3-Hydroxyflavanone (Dihydroflavonol) Phytoalexins from the Papilionate Legume Shuteria vestita

Diffusates from the fungus-inoculated leaflets of Shuteria vestita have yielded four novel 3-hydroxyflavanone (dihydroflavonol) phytoalexins. From spectroscopic and chemical evidence, three of these phytoalexins have been identified as (2R,3R,2''R)--3,5,4'-trihydroxy-2'-isopropenyldihydrofurano (4'',5''; 6,7) flavanone (shuterol,1), (2R,3R)--3,5,7,4'-tetrahydroxy-6-(3,3-dimethylally) flavanone (shuterin, 2), and (2R,3R,2''R)--3,5,2',4'-tetrahydroxy-2''-isopropenyldihydrofurano (4'',5''; 6,7)flavanone (shuterone A, 3). The fourth compound (shuterone B, 4) is considered to be the 2S,3R stereoisomer of shuterone A.