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Author

Amita Kar

Bio: Amita Kar is an academic researcher. The author has contributed to research in topics: Phenanthrene & Bulbophyllum. The author has an hindex of 3, co-authored 3 publications receiving 99 citations.

Papers
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Journal ArticleDOI
TL;DR: Two new polyoxygenated phenanthrene derivatives, confusarin and confusaridin, are isolated from the orchid Eria confusa and are shown to be 2,7-dihydroxy-3,4,8-trimethoxyphenanthrene and 2,6- dihydrox-2,6,7, 8-tetramethoxyrene, respectively.

46 citations

Journal ArticleDOI
TL;DR: Bulbophyllanthrin, a novel phenanthrene derivative from the orchid B. leopardium, was shown to have the structure 1a mainly on the basis of spectral evidence including 13 C and 2D NMR spectra as discussed by the authors.

43 citations

Journal ArticleDOI
TL;DR: The structure of erianol was established as 4α,24,24-trimethylcholesta-7,25-dien-3β-ol from spectral and chemical evidence.

15 citations


Cited by
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Journal ArticleDOI
TL;DR: The present study furnishes an overview of the hydroxy or/and methoxy-substituted 9,10-dihydro/phenanthrene, methylated, prenylated and other monomeric derivatives, dimeric and trimeric phenanthrenes and their biological activities.

282 citations

Journal ArticleDOI
TL;DR: A dicationic phosphine with no spacer between the phosphorus atom and the two positively charged groups is described, which makes its donor ability poorer than that of phosphites and only comparable to extremely toxic or pyrophoric compounds such as PF3 or P(CF3)3.
Abstract: Very often ligands are anionic or neutral species. Cationic ones are rare, and, when used, the positively charged groups are normally appended to the periphery of the ligand. Here, we describe a dicationic phosphine with no spacer between the phosphorus atom and the two positively charged groups. This structural feature makes its donor ability poorer than that of phosphites and only comparable to extremely toxic or pyrophoric compounds such as PF3 or P(CF3)3. By exploiting these properties, a new Au catalyst has been developed displaying a dramatically enhanced capacity to activate π-systems. This has been used to synthesize very sterically hindered and naturally occurring 4,5-disubstituted phenanthrenes. The present approach is expected to be applicable to the development and improvement of many other transition metal catalyzed transformations that benefit from extremely strong π-acceptor ligands. The mechanism of selected catalytic transformations has been explored by density functional calculations.

114 citations

Journal ArticleDOI
TL;DR: Two new phenanthrenes (4,9-dimethoxyphenanthrene-2,5-diol and 4,6-dimethyltoxymethylhexane-1,3,7-triol) and two new 9,10-dihydrophenanthreness (4methoxy-9, 10-dibenzyls and the triterpenoid friedelin were isolated and characterized from the hexane extract of the orchid Bulbophyllum vaginatum) were determined by spectroscopic analyses

94 citations

Journal ArticleDOI
TL;DR: Moscatilin, a new bibenzyl derivative isolated from the orchid Dendrobium moscatum, was shown to have the structure 4,4′-dihydroxy-3,3′,5-trimethoxybibensyl.

81 citations