Sunil Kumar Talapatra

Bio: Sunil Kumar Talapatra is an academic researcher from University of Calcutta. The author has contributed to research in topics: Diterpene & Michelia. The author has an hindex of 16, co-authored 85 publications receiving 747 citations.

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

Abstract: 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.

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.

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.

The shikimate pathway―a metabolic tree with many branches

Abstract: (1990). The Shikimate Pathway — A Metabolic Tree with Many Branche. Critical Reviews in Biochemistry and Molecular Biology: Vol. 25, No. 5, pp. 307-384.

On the origins of triterpenoid skeletal diversity.

Abstract: The triterpenoids are a large group of natural products derived from C(30) precursors. Nearly 200 different triterpene skeletons are known from natural sources or enzymatic reactions that are structurally consistent with being cyclization products of squalene, oxidosqualene, or bis-oxidosqualene. This review categorizes each of these structures and provides mechanisms for their formation.

Prenylated indole derivatives from fungi: structure diversity, biological activities, biosynthesis and chemoenzymatic synthesis

Abstract: Covering: up to mid-2009 Prenylated indole alkaloids are hybrid natural products derived from prenyl diphosphates and tryptophan or its precursors and widely distributed in filamentous fungi, especially in the genera Penicillium and Aspergillus of ascomycota. These compounds represent a group of natural products with diverse chemical structures and biological activities. Significant progress on their biosynthesis has been achieved in recent years by identification of biosynthetic gene clusters from genome sequences and by molecular biological and biochemical investigations. In addition, a series of prenylated indole derivatives have been produced by chemoenzymatic synthesis using overproduced and purified enzymes.

Occurrence and distribution of free flavonoid aglycones in plants

Abstract: Flavonoids are widely present in plants as water-soluble glycosides but the lipophilic free aglycones are far less abundant. The 462 flavonoids reported so far to be present in the free state and their plant sources are listed. Evaluation of these data reveals a correlation in most cases between the occurrence of flavonoid aglycones, the presence of secretory structures and the production of other lipophilic plant products. Their accumulation in some plant organs and in certain taxa is discussed. Special attention is given to their occurrence in materials deposited externally on leaves and buds.