M. Uvais S. Sultanbawa

Distichol an antibacterial polyphenol from Shorea disticha

Abstract The structure of distichol, a new hexadehydrotrimer of resveratrol isolated from the bark of Shorea disticha , has been established on the basis of spectroscopic evidence, chemical degradations and biosynthetic considerations.

1,2(3)-Tetrahydro-3,3′-biplumbagin: A naphthalenone and other constituents from Plumbago zeylanica☆

Abstract The isolation of plumbagin, droserone, isoshinanolone and a new naphthalenone, 1,2(3)-tetrahydro-3,3′-biplumbagin is reported from the phenolic fract

Polyphenols from Stemonoporus species

Abstract Methanol extracts of the bark of six Stemonoporus species have been investigated. A new polyphenol, stemonoporol, has been isolated from four species. The polyphenols, copalliferol A and vaticaffinol are reported for the second time. Formic acid treatment converted stemonoporol to copalliferol A.

Polyphenols from dipterocarp species. Vaticaffinol and ε-viniferin

A dipterocarp endemic to Sri Lanka, Vatica affinis, yielded three phenols. Two of them showed anti-bacterial properties and have been shown to be the dimer and tetramer of 3,5,4′-trihydroxystilbene.

Another antibacterial polyphenol, copalliferol B, from Vateria copallifera (dipterocarpaceae)

Abstract Another new resveratrol trimer, copalliferol B, isolated from Vateria copallifera , has been characterized on the basis of chemical, spectroscopic and biogenetic evidence.

Chemical investigation of ceylonese plants. Part VIII. Trapezifolixanthone, a new di-isoprenylated xanthone from the bark of Calophyllum trapezifolium Thw. (Guttiferae)

From the bark extractives of Calophyllum trapezifolium Thw. calabaxanthone (I), taraxerol, β-simiarenol, β-sitosterol, and a new xanthone, trapezifolixanthone (III) have been isolated. The latter has been shown to be 5,10-dihydroxy-2,2-dimethyl-12-(3-methylbut-2-enyl)pyrano[3,2-b]xanthen-6(2H)-one.

Distribution of some triterpenes and phenolic compounds in the extractives of endemic dipterocarpaceae species of Sri Lanka

Abstract Extractives of bark and/or timber of 11 species belonging to the genera Cotylelobium, Hopea, Shorea , Vateria and Vatica yielded a fatty-acid ester, a sitosteryl ester, β-amyrin acetate, β-amyrin, dipterocarpol, ursolic acetate, lupeol, sitosterol, ursolic acid, betulinic acid, hexamethyl-coruleoellagic acid, tetramethylellagic acid, chrysophanol and scopoletin. The distribution of these compounds in 18 other species was examined by TLC screening.

Chemical investigation of ceylonese plants. Part VII. Extractives of Calophyllum thwaitesii Planch and Triana and Calophyllum walkeri Wight (Guttiferae)

The bark and timber extractives of C. thwaitesii Planch and Triana and C. walkeri Wight have been studied. The former contained taraxerol and friedelin in the bark whilst the latter had taraxerol and β-simiarenol. In addition a new di-isoprenylated xanthone, named thwaitesixanthone, has been isolated from the former and shown to be 13-hydroxy-3,3,10,10-tetramethyl-3H,10H-dipyrano[3,2-a:2′,3′-i]xanthen-14-one (IV) while calabaxanthone, 5-hydroxy-8-methoxy-2,2-dimethyl-7-(3-methylbut-2-enyl)-2H-pyrano[3,2-b]xanthen-6-one (I) was isolated from the latter. The timber extractives of both species gave 1,5-dihydroxyxanthone, 1,7-dihydroxyxanthone, jacareubin (IIa), and β-sitosterol. The latter species also contained guanandin (VIII), 1,3,5-trihydroxy-2-(3-methylbut-2-enyl)xanthone (X), and the new metabolite 1,5-dihydroxy-2,3-dimethoxyxanthone (IX).

A stereospecific route to trisubstituted olefins viaβ-lactones

Diastereoisomeric αα-disubstituted β-hydroxy-acids have been converted into β-lactones, which on refluxing in collidine yielded E- or Z-olefins with high stereoselectivity. The mechanisms of these transformations are discussed.

Chemical investigation of ceylonese plants. Part XII. (+)-3,4′,5,7-Tetrahydroxy-3′-methoxyflavanone [(+)-dihydroisorhamnetin] and 3,5,7-trihydroxy-3′,4′-dimethoxyflavone (dillenetin): two new natural products from Dillenia indica L.

The title compounds [(I) and (III)] have been obtained from the bark and pericarp of Dillenia indica L., respectively.