Prenylated flavonoids in the roots of yellow lupin.

A further investigation of the methanol-soluble compounds in yellow lupin roots has revealed a new diprenylchromone, a new coumaronochromone (lupinalbin H), a new isoflavone 5,7,4'-trihydroxy-8,3'-di-(3,3-dimethylally)isoflavone (isolupalbigenin), and some complex flavanones. The latter compounds have been identified as two known diprenylated flavanones (lonchocarpol A and euchrestaflavanone A), two diasteroisomeric pairs of dihydrofuranoflavanones (lonchocarpols C1 and C2, and lonchocarpols D1 and D2, the structures formerly proposed for lonchocarpols C and D were also reinvestigated), a new furanoflavanone (lupinenol), and three 8-prenylflavanones with an additional (2RS)-hydroxy-3-methyl-3-butenyl side chain. The structures of the latter flavanones were unambiguously identified by spectroscopic (1H NMR) comparison with 6-, 8- and 3'-prenylnaringenins chemically prepared from (2S)-naringenin. The antifungal activity of the prenylated naringenins, and of the various yellow lupin flavanones, was determined by TLC place bioassays using Cladosporium herbarum as the test fungus.

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.

A New isoflavanone phytoalexin from Medicago rugosa.

An isoflavonoid phytoalexin produced by the fungus-inoculated leaflets of Medicago rugosa Desr. has been formulated as (+/-)-7,4'-dimethoxy-2'-hydroxyisoflavanone (isosativanone). This compound cooccurs with the known isoflavonoid fungitoxins, (-)-medicarpin, (-)-vestitol, (-)-isosativanand(+/-)-vestitone.

Induced isoflavonoids from fungus-infected stems of pigeon pea (Cajanus cajan).

Four antifungal isoflavones [7-hydroxy-4'-methoxy-(1); 5,7,4'-trihydroxy-(2); 5,7,2',4'-tetrahydroxy-(3); 5,2',4'-trihydroxy-7-methoxy-(4)] and one isoflavanone [(5,2'-dihydroxy-7,4'-dimethoxy-(7)] have been isolated from the fungus-infected stems of Cajanus cajan. A sixth compound has been provisionally identified as 5,2'-dihydroxy-7,4'-dimethoxyisoflavone (5). The structure of 5,2'-dihydroxy-7,4'-dimethoxyisoflavanone (cajanol) was confirmed by synthesis from ferreirin (5,7,2'-trihydroxy-4'-methoxyisoflavanone).