Variabilin,a 6a-hydroxypterocarpan from Dalbergia variabilis

Bark and wood of the creeper Dalbergia variabilis contain the previously described friedelin, O-acetyl-oleanolic acid, formononetin, 8-O-methylretusin, (+)-vestitol, (±)-mucronulatol, (+)- and (±)-medicarpin, besides (+)-variabilin [(6aR,11aR)-6a-hydroxy-3,9-dimethoxypterocarpan]. This structure was confirmed by the conversion of (+)-variabilin into di-O-methylcoumestrol.     

Structures of some minor pterocarpans of Neorautanenia edulis

The constitution of five new compounds, (?)-neorautenol, (?)-neodunol, (?)-homoedudiol, neorauteen and neoduleen, has been established in the root bark of Neorautanenia edulis.     

A chemical dichotomy in phytoalexin induction within the tribe vicieae of the leguminosae

Using either leaf or cotyledon tissues, the phytoalexin response of over 60 representative members of the genera Lathyrus, Lens, Pisum and Vicia was determined. Twenty-nine Vicia species produced furanoacetylenes, as did the two Lens species examined. By contrast, Pisum and Lathyrus failed to produce any of these phytoalexins, but formed pisatin instead. Thus, pisatin was formed as the major phytoalexin in 29 of 31 Lathyrus species tested, representing 10 sections within the genus. This dichotomy in phytoalexin response is discussed in relation to the taxonomy of the tribe Vicieae.     

Phytoalexin induction and its chemosystematic significance in the genus Trigonella

Using the drop-diffusate technique, a number of isoflavonoid phytoalexins have been obtained from the excised, fungus-inoculated leaflets of 41 species belonging to the legume genus Trigonella. Leaf diffusates variously contained pterocarpan (medicarpin and maackiain) and isoflavan (vestitol and sativan) derivatives previously associated with genera closely allied to Trigonella. In diffusates from T. calliceras, medicarpin was accompanied by a phytoalexin (designated TC-1) provisionally identified as a new hydroxylated pterocarpan. Most of the Trigonella species were also examined for their ability to release coumarin upon tissue maceration. The combined phytoalexin/coumarin data suggest that three major intrageneric chemical divisions occur in Trigonella; two of these apparently link the genus to Medicado/Factorovskya and Melilotus respectively, whilst the third provides some evidence for a connection with Trifolium. The taxonomic aspects of these findings are discussed in the light of earlier morphological studies which provided evidence for a distinct floral dichotomy amongst Trigonella species.     

膜荚黄芪中的紫檀烷和异黄烷化合物

前文[1]报道了从膜荚芪（Astragalus membranaceus(Fish.)Bunge）根的乙醇提取物中分离得到的2     

Isoflavanoids of dalbergia Oliveri

The heartwood of Dalbergia oliveri has yielded 11 natural products of which two are new 3-phenylcoumarins. The structures of the extractives have been examined by physical methods and in addition the assigned structures have been confirmed by synthesis. The oxygenation pattern relating the structures of chalcone, isoflavone, pterocarpans, 3-arylcoumarins, coumestones and the isoflavan and isoflavanone suggests a common biosynthetic origin.     

Isoflavonoid and stilbene phytoalexins of the genus Trifolium

The fungus-inoculated leaflets of 55 Trifolium species have been examined for the presence of isoflavonoid and non-flavonoid phytoalexins. Isoflavonoid derivatives belonging to the pterocarpan (medicarpin, maackiain and 4-methoxymaackiain) and isoflavan (vestitol, isovestitol, sativan, isosativan and arvensan) classes were isolated from 50 species whilst T. campestre and T. dubium accumulated the trihydroxy stilbene, transresveratrol. Three other species (T. badium, T. scutatum and T. spadiceum) apparently did not produce phytoalexins in response to fungal inoculation. The distribution and biosynthetic relationship of Trifolium phytoalexins is discussed and the genus compared with others belonging to the Trifolieae and related tribes.     

Phytoalexin production by Ononis species

Following exposure to short wavelength (254 nm) ultra-violet light, the detached leaflets of Passaea (Ononis) ornithopodioides and 31 species and subspecies of Ononis have been found to accumulate substantial quantities of the isoflavonoid (pterocarpan) phytoalexin, medicarpin. Apart from P. (Ononis) ornithopodioides, O. cristata, O. fruticosa, O. pubescens and O. rotundifolia, leaf tissues of all the species investigated similarly contained small amounts of the related fungitoxic pterocarpan, maackiain. Isoflavan phytoalexins common in genera such as Medicago and Trifolium (tribe Trifolieae) were absent from both Ononis and Passaea. The phytoalexin data suggest that Passaea should probably be combined with Ononis and, in conjunction with information on constitutive isoflavonoids, that Ononis itself should be assigned to the Trifolieae rather than to the distinct tribe Ononideae. Chemical evidence for and against an especially close taxonomic association between Ononis and Cicer (tribe Cicereae) is also briefly discussed.     

Identification of the Erythrina phytoalexin cristacarpin and a note on the chirality of other 6a-hydroxypterocarpans

Cristacarpin, a new phytoalexin from Erythrina crista-galli is assigned the structure (?)-3,6a-dihydroxy-9-methoxy-10-γ,γ-dimethylallyl-cis-pterocarpan. It is accompanied by the known phytoalexins phaseollidin and demethylmedicarpin in this plant. Cristacarpin, phaseollidin and demethylmedicarpin were also obtained from E. sandwicensis and (together with isomedicarpin) from the related legume, Psophocarpus tetragonolobus. A compilation of selected optical rotation, NMR and conformational data for all known 6a-hydroxypterocarpans is presented and it is concluded that the previously assigned chiralities of neobanol, glyceollins I–IV and 3,6a,9-trihydroxypterocarpan should be reversed. Chirality assignments are made for a number of previously unassigned compounds.