Ajit K. Chakravarty

Bacopaside I and II: two pseudojujubogenin glycosides from Bacopa monniera.

Two saponins, designated as bacopaside I and II, have been isolated from Bacopa monniera Wettst. and their structures have been elucidated as 3-O-alpha-L-arabinofuranosyl-(1-->2)-[6-O-sulphonyl-beta-D-glucopyranosyl-(1-->3)]-alpha-L-arabinopyranosyl pseudojujubogenin (1) and 3-O-alpha-L-arabinofuranosyl-(1-->2)-[beta-D-glucopyranosyl (1-->3)]-beta-D-glucopyranosyl pseudojujubogenin (2) mainly on the basis of 2D NMR and other spectral analyses.

Carbazole alkaloids from roots of Glycosmis arborea

Abstract A new carbazole alkaloid, designated as glycoborinine, was isolated from the roots of Glycosmis arborea , along with two other known carbazole alkaloids, viz. glycozoline and glycozolidine, and two known quinoline alkaloids, viz. skimianine and 3- (3′,3′-dimethylallyl)-4,8-dimethoxy- N -methylquinolin-2-one. Its structure was elucidated mainly on the basis of its 2D NMR spectral analyses.

Bacopasaponins E and F : two jujubogenin bisdesmosides from Bacopa monniera

Two new dammarane-type jujubogenin bisdesmosides, bacopasaponins E and F of biological interest have been isolated from the reputed Indian medicinal plant Bacopa monniera and defined as 3-O-[beta-D-glucopyranosyl(1 --> 3)[alpha-L-arabinofuranosyl(1 --> 2)]alpha-L-arabinopyranosyl]-20-O-(alpha-L-arabinopyranosyl) jujubogenin and 3-O-[beta-D-glucopyranosyl(1 --> 3)[alpha-L-arabinofuranosyl(1 --> 2)]beta-D-glucopyranosyl]-20-O-alpha-L-arabinopyranosyl) jujubogenin respectively by spectroscopic methods and some chemical transformations.

Swertane triterpenoids from Swertia chirata

Abstract Two novel triterpenes belonging to swertane skeleton, besides gammacer-16-en-3β-ol and 21α H -hop- 22(29)-en-3β-ol, of rare occurrence have been isolated from Swertia chirata , along with some common triterpenoids. Their structures were established on the basis of spectral and chemical evidence.

Carbanion addition to acetylenes : An efficient stereoselective route to α-methylene-γ-lactams

Abstract Intramolecular addition of carbanions, derived from the acetylenic amides (5b,d) , (7) and (9) has been shown to be highly stereoselective leading to the α-methylene-γ-lactam derivatives (6a,b) , (8a,b) and (10) .

A neolignan and sterols in fruits of Solanum sisymbrifolium

A new neolignan, designated as sisymbrifolin, and carpesterol were isolated from the berries of Solanum sisymbrifolium. Their structures were established mainly on the basis of 2D NMR analyses.

A diterpenoid from roots of Gelonium multiflorum

Abstract A new diterpene diol, along with the three known flavones, kanugin, desmethoxy kanugin and pinnatin, was isolated from the roots of Gelonium multiflorum and its structure was established as ent -kaurene-3β, 15β-diol mainly on the basis of 2D NMR spectral analyses.

Triterpenoid prosaponins from leaves of Maesa chisia var. angustifolia

Abstract Acid hydrolysis of the saponin fraction of the leaves of Maesa chisia var. angustifolia yielded a monoglucoside fraction besides camelliagenin A as a minor constituent. The glucose moiety of the former could be removed by hydrolysis by Smith degradation to yield two new acylated triterpenoids characterised as 16α- O -acetyl-22α- O -angeloyl-camelliagen A and 16α- O -acetyl-22α- O -(2′-methylbutyroyl)-camelliagenin A as well as camelliagenin A and its 22α,28-glycolaldehyde acetal. The possibility of the later acetal derivative being an artefact could not, however, be ruled out.

Simple aromatic amines from justicia gendarussa. 13C NMR spectra of the bases and their analogues

Abstract Four simple 0-disubstituted aromatic amines have been isolated from the leaves of Justicia gendarussa Burm and characterized as 2-amino benzyl alcohol (3), 2-(2′-amino-benzylamino) benzyl alcohol (4) and their respective 0-methyl ethers 1 and 2 from 1H NMR and mass spectral analyses of the bases and their acetates. Structures 3 and 4 have also been confirmed by synthesis. Intramolecular hydrogen bonding (cf. 9, 13 and 14) has been envisaged to explain the unexpected shielding of -CH2-OH carbon signals of 3 4 on acetylation and upfield displacement of -CH2-N signal of 2a vs 4a in their 13C NMR spectra in CDCl3 solution 1JCH values have been found to be useful for the assignment of aromatic methine carbon signals in o-disubstituted compounds. Part 68 of the series Studies on Indian medicinal plants. For Part 67, see P. K. Dutta, D. Bagchi and S.C. Pakrashi, Indian J. Chem. in press.

Solanolide, a steroid lactone sapogenin from Solanum hispidum☆

Abstract Solanolide, a new C 22 steroid lactone sapogenin isolated from the leaves of Solanum hispidum Pers., has been characterized as 3β, 6α, 16β-trihydroxy-5α-pregnane-20 S -carboxylic acid (22, 16)-lactone from 1 H and 13 C NMR analyses and correlation with neochlorogenin.