Piyali Sengupta

Bio: Piyali Sengupta is an academic researcher from University of Calcutta. The author has contributed to research in topic(s): Cycloaddition & Aryl. The author has an hindex of 4, co-authored 14 publication(s) receiving 63 citation(s).

Amides from Piper brachystachyum and Piper retrofractum.

Abstract: Three unsaturated amides, designated brachystamides-C, D and E have been characterised from Piper brachystachyum Wall. Brachystamide-C, shown to be N-isobutyl-15-(3',4'-methylenedioxyphenyl)-2E,4E,13E-pentadecatrienamide, was unusual in having a non-conjugated double bond. Piper retrofractum Vahl. yielded retrofractamide-D, which has been fully characterised.

The first report of unusual flipping of the cycloadducts from 1,3-dipolar cycloaddition of 3,4,5,6-tetrahydropyridine N-oxide to N-cinnamoyl piperidines

Abstract: A series of cycloadducts possessing unusual flipping modes have been isolated from the 1,3-dipolar cycloaddition of 3,4,5,6-tetrahydropyridine N-oxide to piperidides of cinnamic acid and para-substituted cinnamic acids and these were analyzed by X-ray crystallography to reveal novel solid-state structures. The presence of two different flippomers arising due to flipping of the six/five bicyclic ring was confirmed both in solid state and in solution. This is the first observation of 1,3-dipolar cycloadducts having two different flippomers arising due to flipping of the isoxazolidine ring.

Synthetic and spectroscopic studies of structural analogues of piper amides — the 5-aryl-2e,4e-pentadienamides.

Abstract: The methyl esters and piperidides of fourteen 5-aryl-2E,4E-pentadienoic acids have been synthesized starting from the corresponding aryl aldehydes.

Petrogenesis of flood basalts of the Narsingpur-Harrai-Amarwara-Lakhnadon section of eastern deccan province, India

Abstract: The present area of investigation falls in the Eastern Deccan segment where available field and geochemical data are rather limited. In the present study, five distinctive structural zones namely Lower Vesicular zone, Lower Colonnade Zone, Entablature Zone, Upper Colonnade Zone and Upper Vesicular Zone have been identified in different lava flows which are helpful for the purpose of stratigraphic correlation. All the lavas under investigation can be classified into three distinct geochemical groups (viz. Group I, Group 2 and Group 3) on the basis of their Mg′ number and TiO2 wt%. The Group 1 lavas are marked by low Mg′ No (0.39–0.45) and high TiO2 (2.9–3.6 wt%) while Group 2 lavas are characterized by moderate Mg′ No (0.45–0.50) and moderate TiO2 (2.4–2.9 wt%). On the other hand, high Mg′ No (0.49–0.54) and low TiO2 (1.91–2.31 wt%) characterize the Group 3 basalts. Interestingly, the basaltic flows corresponding to three distinct groups are intermixed with each other; in other words, lava flows belonging to several groups are juxtaposed with one another with increasing height.

Recent studies on 1,3-dipolar cycloadditions of nitrones

Abstract: A new synthesis of 2 , 2 - dimethyl - 12 - [ 3 - methylbut - 2 - enyl ] - 2H , 6H - pyrano [ 3 , 2 - b ] xanthen - 6 - one (7) is described from 1 , 3 - dihydroxyxanthone and involved the preparation of a linear dihydropyranoxanthone (26), its conversion into the pyranoxanthone (14) and its prenylated derivative (31) followed by a Claisen rearragement leading to the target substrate (7).

Isolation, Synthesis, and Evolutionary Ecology of Piper Amides

Abstract: The phytochemistry of the genus Piper is rich in terms of numbers of compounds discovered, but given the diversity of this genus and the intraspecific diversity of secondary metabolites in those species that have been examined, Piper chemistry has not been adequately investigated. The natural products chemistry that has been elucidated is well documented and has been the subject of extensive review (Sengupta and Ray 1987, Parmar et al. 1997). Since those reviews were published, 28 new species have been investigated (Benevides et al. 1999, Chen et al. 2002, Ciccio 1997, de Abreu et al. 2002, Dodson et al. 2000, dos Santos et al. 2001, Facundo and Morais 2003, Jacobs et al. 1999, Joshi et al. 2001, Martins et al. 1998, Masuoka et al. 2002, McFerren and Rodriquez 1998, Moreira et al. 1998, Mundina et al. 1998, Srivastava et al. 2000a, Stohr et al. 2001, Terreaux et al. 1998, Torquilho et al. 2000, Vila et al. 2001, 2003, Wu et al. 1997), and 69 compounds new to Piper have been discovered (Adesina et al. 2002, Alecio et al. 1998, Baldoqui et al. 1999, Banerji et al. 1993, 2002b, Boll et al. 1994, Chen et al. 2002, Ciccio 1997, Da Cunha and Chaves 2001, Das and Kashinatham 1998, daSilva et al. 2002, de Araujo-Junior et al. 1997, Dodson et al. 2000, Gupta et al. 1999, Jacobs et al. 1999, Joshi et al. 2001, Martins et al. 1998, Masuoka et al. 2002, Menon et al. 2000, 2002, Moreira et al. 1998, 2000, Mundina et al. 1998, Navickiene et al. 2000, Pande et al. 1997, Parmar et al. 1998, Santos and Chaves 1999a,b, Santos et al. 1998, Seeram et al. 1996, Siddiqui et al. 2002, Srivastava et al. 2000a,b, Stohr et al. 1999, Terreaux et al. 1998, Wu et al. 2002a,b, Zeng et al. 1997).

Oxidative cyclization of 3-oxopropanenitriles with α,β-unsaturated amides by manganese(III) acetate. Regio- and stereoselective synthesis of 4-cyano-2,3-dihydrofuran-3-carboxamides

Abstract: 4-Cyano-2,3-dihydrofuran-3-carboxamides were obtained from the oxidative cyclization of 3-oxopropanenitriles with unsaturated amides using manganese(III) acetate. Treatment of 3-oxopropanenitriles with (2E)-3-(5-methyl-2-furyl)acrylamide and (2E)-3-(2-thienyl)acrylamide gave 2-(5-methyl-2-furyl) and 2-(2-thienyl) substituted 4-cyano-2,3-dihydrofuran-3-carboxamides in moderate yields, respectively. However, (2E)-3-(2-furyl)acrylamide and (2E)-3-phenylacrylamide did not produce any product under the same conditions. On the other hand, reaction of a dienamide such as (2E,4E)-5-phenylpenta-2,4-dienamide with 3-oxopropanenitriles gave diastereomeric mixtures of 2-(2-vinylphenyl)-4-cyano-2,3-dihydrofuran-3-carboxamides. Mechanisms are proposed for the formation of all of these compounds.