Avijit Banerji

Occurrence of geissoschizine and other minor biogenetically related alkaloids in Rhazya stricta

Abstract Chemical investigation of Rhazya stricta Decaisne has led to the isolation of more than a dozen indole alkaloids. Two more indolic bases, rhazinine and R1, obtained from this plant, were shown to be identical with antirhine and geissoschizine respectively. The biogenetic significance of the occurrence of the latter is discussed. Four other minor indole alkaloids, viz. R2, R3, rhazinilam and rhazinaline are also present.

Antidiarrhoeal activity of carbazole alkaloids from Murraya koenigii Spreng (Rutaceae) seeds

The bioassay guided fractionation of the n-hexane extract of the seeds of Murraya koenigii Spreng (Rutaceae) resulted in the isolation of three bioactive carbazole alkaloids, kurryam (I), koenimbine (II) and koenine (III). The structures of the compounds were confirmed from their (1)H-, (13)C-, and 2D-NMR spectral data. Of the three compounds (I) and (II) exhibited significant inhibitory activity against castor oil-induced diarrhoea and PGE(2)-induced enteropooling in rats. The compounds also produced a significant reduction in gastrointestinal motility in the charcoal meal test in Wistar rats.

Aurantiamides: A new class of modified dipeptides from Piper aurantiacum

Abstract Two new amides, aurantiamide and aurantiamide acetate, were isolated from Piper aurantiacum. Their structures were determined as N-(N′-benzoyl-S-phenylalaninyl)-S-phenylalaninol and its acetate, respectively, from chemical and spectroscopic studies. The structures and stereochemistry were confirmed by synthesis. The corresponding diastereoisomers were also synthesized and their spectroscopic properties compared with those of the natural compounds.

Structural and synthetic studies on the retrofractamides—amide constituents of Piper retrofractum

Abstract Two new unsaturated amides, retrofractamides A and C, were isolated from the total above-ground parts of Piper retrofractum . Retrofractamide A was shown to be N -isobutyl-9(3′,4′-methylenedioxyphenyl)2 E ,4 E ,8 E -nonatrienamide from spectroscopic and chemical investigations. The structure 6 for retrofractamide C was suggested from spectroscopic and chemical studies and was confirmed by a total stereoselective synthesis. The presence of sesamin and 3,4,5-trimethoxydihydrocinnamic acid as well as two higher homologues of retrofractamide A, viz. pipericide (retrofractamide B) and retrofractamide D was demonstrated. The synthesis of pipericide was also achieved.

Two amides from piper Brachystachyum

Abstract Two new unsaturated amides, brachystamides-A and B, were isolated from the total above-ground parts of Piper brachystachyum. Brachystamide-A was shown to be N-isobutyl-15 (3′,4′-methylenedioxyphenyl) 2E,4E-pentadecadienamide from spectroscopic and chemical investigations. Brachystamide-B was N-isobutyl-15 (3′,4′-methylenedioxyphenyl) 2E,4E,14E-pentadecatrienamide.

Scholarine: An indole alkaloid of Alstonia scholaris

Abstract A new alkaloid designated scholarine was isolated from the leaves of Alstonia scholaris . It was (±) 12-methoxyechitamidine as determined by chemical and spectroscopic investigations.

Cycloaddition of C,N-diarylnitrones to 2-butenolide : Synthesis of 2,3,6,6a-tetrahydrofuro[3,4-d] isoxazol-4 (3aH)-one

Abstract The cycloadditions of four C,N-diaryl nitrones (1–4) to the 5-membered conjugated lactone 2-butenolide were investigated. Two stereoisomeric 2-phenyl-3-aryl-2,3,6,6a-tetrahydrofuro[3,4- d ]-isoxazol-4(3a H )-one cycloadducts and a ring-opened butanolide derivative were obtained in each case. The structure and stereochemistry of the products were determined by detailed NMR studies. The regiochemical course of the cycloadditions is explained, and the genesis of the ring-opened product rationalised.

Sylvone, a new furanoid lignan of Piper sylvaticum

Abstract The structure of a novel 2,3,4- trisubstituted furanoid lignan, designated sylvone, was established as 1 from detailed spectroscopical and chemical studies.

Saradaferin, a new sesquiterpenoid coumarin from Ferula assafoetida

Phytochemical investigation of the gum resin of Ferula assafoetida resulted in the isolation and characterization of a new sesquiterpenoid coumarin, Saradaferin (1) named as [Decahydro-(3-α-hydroxy-4,4,10-trimethyl-8-methylene-9-naphthenyl)-α-hydroxymethyl] ether of umbelliferone.

Studies on single-electron transfer reagents. Part IV reaction of nitrogen heterocycles with sodium naphthalenide

Abstract Reactions of several nitrogen heterocycles with sodium naphthalenide in aprotic solvents were investigated. The reactions were quenched with an aqueous buffer. Quinoline reacted by the single-electron transfer pathway to give a ‘dimeric’ (3), a ‘trimeric’ product (4) and 4-quinolone. 4-Quinazolinone afforded a single ‘dimeric’ product (9). Reaction of isoquinoline in monoglyme gave three ‘dimeric’ products and 4-hydroxy isoquinoline. N-Methyl oxindole gave a ‘dimeric’ and two ‘trimeric’ products. The structure of the products were established by spectroscopical techniques including two-dimensional NMR studies.