Asok K. Mallik

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.

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.

A chromenoflavanone and two caffeic esters fromPongamia glabra

Abstract (−)Isoglabrachromene, a new natural chromenoflavanone, and hexacosanyl caffeate and triacontanyl caffeate, two new esters, have been isolated together with 11 known flavonoids and betulinic acid from the stem bark of Pongamia glabra . The reason why the H-α and H-α of 2′-hydroxy-6′-methoxychalcones appear at the same field in their 1 H NMR spectra is discussed.

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.

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.

An easy construction of 8,12-dioxa-13-azatricyclo[8.3.1.02,7]tetradeca-2(7),3,5,13-tetraen-14-ones

Abstract 8,12-Dioxa-13-azatricyclo[8.3.1.0 2,7 ]tetradeca-2(7),3,5,13-tetraen-14-ones are obtained in moderate yield by treatment of oximes of o -allyloxyacetophenones with [hydroxy(tosyloxy)iodo]benzene in acetonitrile.

A convenient, eco-friendly, and efficient method for synthesis of bis(3-indolyl)methanes “on-water”

Abstract A convenient, eco-friendly, and efficient method for synthesis of bis(3-indolyl)methanes by the reaction of indoles with various aromatic aldehydes “on-water” has been developed. The attractive features of this method are that in cases of aldehydes which are easily oxidized to acids, no external catalyst is necessary while in other cases a trace amount (ca. 5 mol%) of commercially available and inexpensive catalyst benzoic acid is sufficient to give good to excellent yield of products.

A facile transformation of E-3-benzylideneflavanones to 3-(α-hydroxybenzyl) flavones

During reaction of E-3-benzylideneflavanones with NBS/dibenzoyl peroxide in CCl4 3-(α-hydroxybenzyl) flavones are formed, possibly through involvement of moisture.

Novel formation of 6-acyl-5-(2-pyrrolyl)-3H-pyrrolizines by base-catalysed condensation of pyrrole-2-aldehyde with methyl ketones

Abstract Pyrrole-2-aldehyde undergoes condensation with methyl ketones in aqueous ethanolic alkali in a 2:1 mole ratio yielding 6-acyl-5-(2-pyrrolyl)-3 H -pyrrolizines as novel products in moderate yield.

An efficient synthesis of 1,3-dimethyl-5-(2-phenyl-4H-chromen-4-ylidene) pyrimidine-2,4,6(1H,3H,5H)-triones and investigation of their interactions with β-lactoglobiulin

An efficient method for synthesis of 1,3-dimethyl-5-(2-phenyl-4H-chromen-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-triones has been developed by treatment of 2-hydroxychalcones and 1,3-dimethylbarbituric acid in refluxing toluene in the presence of amberlyst-15 as catalyst in air. The process involves the occurrence of a domino sequence of Michael addition, cyclization and aerial oxidation. The compounds synthesized showed an interesting property of free rotation around the bond linking the two heterocyclic moieties and three of them were found to show binding property with the milk protein β-lactoglobulin (β-lg). DFT and docking (with β-lg) studies of one of the compounds have been done.