Sunil K. Talapatra

Pongaglabol, a new hydroxyfuranoflavone, and aurantiamide acetate, a dipeptide from the flowers of Pongamia glabra.

Abstract Pongaglabol, a new hydroxyfuranoflavone, and aurantiamide acetate, a rarely occurring modified phenylalanine dipeptide, have been isolated together with 4 furanoflavones, karanjin, lancheolatin B, kanjone and pinnatin, a simple flavone, kanugin, a chromenoflavanone (−)-isolonchocarpin, two furanodiketones pongamol and ovalitenone, and β-sitosterol from the petrol and chloroform extracts of the flowers of Pongamia glabra . The structure of pongaglabol has been established as 5-hydroxyfurano(8,7-4″,5″)flavone on the basis of spectral and chemical evidence.

(−)-Regiolone, an α-tetralone from Juglans regia: structure, stereochemistry and conformation

A new α-tetralone derivative designated (−)-regiolone has been isolated with juglone, betulinic acid and sitosterol from the stem-bark of Juglans regia. (−)-Regiolone has been shown to be 4,8-dihydroxy-1-tetralone on the basis of its spectral data and chemical transformation to juglone. Its conformation has been deduced from the 1H NMR spectral data. The absolute stereochemistry of its only chiral centre has been shown to be S by the application of the dibenzoate chirality rule.

Isopongaglabol and 6-methoxyisopongaglabol, two new hydroxyfuranoflavones from Pongamia glabra

Abstract Isopongaglabol and 6-methoxyisopongaglabol, two new hydroxyfuranoflavones, together with two furanoflavones 5-methoxyfurano(8,7-4″,5″)flavone and 5-methoxy-3′,4′-methylenedioxyfurano(8,7-4″,5″)flavone, two simple flavones, desmethoxykanugin and fisetin tetramethyl ether, a chromenoflavanone, ovalichromene B, two triterpenes, cycloart-23-ene-3β,25-diol and friedelin, and β-sitosterol-β- d -glucoside were isolated from the petrol and CHCl 3 extracts of the flowers of Pongamia glabra . The structures of isopongaglabol and 6-methoxyisopongaglabol have been established as 4′-hydroxyfurano(8,7-4″,5″)flavone and 4′-hydroxy-6-methoxyfurano(8,7-4″,5″)flavone, respectively, on the basis of the spectral evidence and they have been confirmed by synthesis.

The structure and biogenetic origin of (-) halicyclamine B from a Xestospongia sponge

Abstract A new tetracyclic diamine, (-) halicyclamine B (1), has been isolated from the sponge Xestospongia sp. and its structure was elucidated from NMR and X-ray crystallography data. Some biogenetic relationships are proposed between 1 and other polycyclic diamines recently reported from sponges.

Aristololactams of Goniothalamus sesquipedalis wall. revised structures of the 2-oxygenated aristololactams

Abstract Goniopedaline, a new phenanthrene lactam, aristololactam A-II and its N,O-diacetyl derivative, taliscanine (second natural occurrence), aurantiamide acetate and β-sitosterol and its β- d -glucoside have been isolated from the leaves and twigs of Goniothalamus sesquipedalis. The structure of goniopedaline has been established from its spectral evidence as 10-amino-3-hydroxy-2,4-dimethoxyphenanthrene-1-carboxylic acid lactam. The structures of aristololactam CII, CIII, DII and DIII have been revised from the previously suggested 3-hydroxymethyl-2-methoxy derivatives and the 3-carboxy-2-hydroxy derivatives to the 2-hydroxymethyl-3-methoxy derivatives and the 2-carboxy-3-hydroxy derivatives respectively based on a careful analysis of their 13C NMR spectral data. Thus, goniopedaline is the only 2-oxygenated aristololactam known so far. This constitutes the first report of the phenanthrene lactams from the Goniothalamus genus.

On the chemistry of indian orchidaceae plants—II1: Dengibsin and dengibsinin, the first natural fluorenone derivatives from dendrobium gibsonii lindl

Abstract Dendrobium gibsonii, an Orchidaceae plant yielded the first natural fluorenone derivatives designated dengibsin and dengibsinin to which 1,5-dihydroxy-7-methoxy-9-fluorenone (1) and 1,6-dihydroxy-5, 7-dimethoxy-9-fluorenonc (2) structures have been assigned respectively. The structures are fully supported by the 1H-NMR, IR, UV and MS spectral data of dengibsin and dengibsnin and a number of their pertinent derivatives. Aurantiamide acetate, dimethyl terephthalate and β-sitosterol have been isolated as the other constituents.

Two pentacyclic triterpenes from Rubia cordifolia

Abstract Rubicoumaric acid and rubifolic acid isolated from Rubia cordifolia have been shown to be 30-hydroxy-3β-p-hydroxycoumaryloxy-urs-12-ene-28-oic acid and 3β,30-dihydroxy-urs-12-ene-28-oic acid(30-hydroxyursolic acid) respectively on the basis of 1H NMR, 13C NMR and mass spectral and chemical evidence.

Defuscin, a new phenolic ester from Dendrobium fuscescens: Conformation of shikimic acid

Abstract Defuscin, a new phenolic ester shown to be n -triacontyl p -coumarate, and (−)-shikimic acid have been isolated from the whole plant of Dendrobium fuscescens Griff. The 1 H NMR spectrum of shikimic acid is indicative of the weighted average of its two half-chair conformers, the one with 4-OH and 5-OH in equatorial orientations being the major contributor.

The structure and stereochemistry of murrangatin : A new monomeric coumarin from Murraya elongata Alph. DC.

Abstract The structure 1 for murrangatin, a new monomeric coumarin isolated from the leaves of Murraya elongata has been elucidated by spectroscopic and chemical evidence, and confirmed by its chemical correlation with phebalosin (7) suggesting its stereochemistry as 1 or its mirror image.

Lagerenyl acetate and lagerenol two tetracyclic triterpenoids with the cycloartane skeleton from Lagerstroemia lancasteri

Abstract Lagerenyl acetate and lagerenol two new tetracyclic triterpenoids with the cycloartane skeleton together with four other triterpenoids 2α-hydroxy- 3β-E-p-coumaryloxy-urs-12-en-28-oic acid (jacoumaric acid, isolated as its monoacetylmethylcarboxylate derivative), 2α-hydroxyursolic acid (isolated as its diacetate), germanicyl acetate and friedelin, and sitosterol were isolated from the leaves and twigs of Lagerstroemia lancasteri. The structures of lagerenyl acetate and lagerenol were established as 3β-acetoxycycloart-24-one and 3β-hydroxycycloart-24-one, respectively, on the basis of spectral and chemical evidence.