Thunalbene, a new stilbene derivative, was isolated from the orchid Thunia alba which also afforded six known stilbenoids: batatasin-III, lusianthridin, 3,7-dihydroxy-2,4-dimethoxyphenanthrene, 3,7-dihydroxy-2,4,8- trimethoxyphenanthrene, cirrhopetalanthrin and flavanthrin. The structure of thunalbene, the first stilbene derivative isolated so far from an Orchidaceae plant, was established as 3,3'-dihydroxy-5-methoxystilbene from spectral and chemical evidence.

SYAMAL CHAKRABORTY

Chemistry

P L MAJUMDER

M ROYCHOWDHURY

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Thunalbene, a stilbene derivative from the orchid Thunia alba

Phytochemistry

Agrostophyllinol and agrostophyllinone, two new triterpenoids, were isolated from the orchid Agrostophyllum brevipes. Agrostophyllinone was also isolated from another orchid Agrostophyllum callosum. The structures of agrostophyllinol and agrostophyllinone were established as 24-methylene-lanosta-9(11)-en-3β-ol (5a) and 24-methylene-lanosta-9(11)-en-3-one (5c), respectively, from spectral and chemical evidence. The above triterpenoids are of considerable biogenetic importance. © 2002 Elsevier Science Ltd. All rights reserved.

Triterpenoids from the orchids Agrostophyllum brevipes and Agrostophyllum callosum

Coeloginanthridin, a 9,10-dihydrophenanthrene derivative, and coeloginanthrin, the corresponding phenanthrene analogue, were isolated from the orchid Coelogyne cristata which earlier afforded coelogin (1a) and coeloginin (1b). The structures of coeloginanthridin and coeloginanthrin were established as 3,5,7-trihydroxy-1,2-dimethoxy-9,10-dihydrophenanthrene (2a) and 3,5,7-trihydroxy-1,2-dimethoxyphenanthrene (2c), respectively, from spectral and chemical evidence including the conversion of coeloginanthridin triacetate (2b) to coeloginanthrin triacetate (2d) by dehydrogenation with DDQ. In the light of earlier reports on structurally similar compounds, 2a and 2c may have biological activities of phytoalexins and endogenous plant growth regulators. © 2001 Published by Elsevier Science Ltd.

Phenanthrene derivatives from the orchid Coelogyne cristata

Reptanthrin and isoreptanthrin, two new dimeric phenanthrenes, were isolated from the orchid Bulbophyllum reptans which also afforded nine known stilbenoids, viz. gymnopusin (1a) [2,7-dihydroxy-3,4,9- trimethoxyphenanthrene], confusarin (1c) [2,7-dihydroxy-3,4,8- trimethoxyphenanthrene], 2,7-dihydroxy-3,4,6-trimethoxyphenanthrene (1d) and its 9,10-dihydro derivative, flavanthrinin (1e) [2,7-dihydroxy-4- methoxyphenanthrene] and its 9,10-dihydro derivative (coelonin), 3,3'- dihydroxy-5-methoxybibenzyl (batatasin-III), cirrhopetalanthrin (2a) [2,2',7,7'-tetrahydroxy-4,4'-dimethoxy-1,1'-biphenanthryl] and its 9,9',10,10'-tetrahydro derivative (flavanthrin). The structures of reptanthrin and isoreptanthrin were established as 2,2',7,7'-tetrahydroxy- 3,3',4,4',9,9'-hexamethoxy-1,1'-biphenanthryl (2c) and 2,2',7,7'- tetrahydroxy-3,3',4,4',9,9'-hexamethoxy-1,8'-biphenanthryl (3a), respectively, from spectral and chemical evidence including their biomimetic synthesis from the congener 1a with phosphomolybdic acid (PMA) on silica gel.

Dimeric phenanthrenes from the orchid Bulbophyllum reptans

The structures of agrostonin and agrostonidin, two new dimeric phenanthrene derivatives isolated from the orchids, Agrostrophyllum khasiyanum and A. callosum, were established as 2,2',7,7'-tetrahydroxy- 4,4',6,6'-tetramethoxy-1,1'-biphenanthryl and 2,2',6,6'-tetrahydroxy- 4,4',7,7'-tetramethoxy-1,1'-biphenanthryl, respectively, from spectral and chemical evidence, including regioselective biomimetic synthesis from their respective 9,10-dihydro monomers by oxidative coupling with phosphomolybdic acid (PMA) on a silica gel surface.

Dimeric phenanthrenes from two Agrostophyllum species

A new dihydrochalcone derivative, lusianin, two other known chalcones and a phenanthrene derivative were isolated from the orchid Lusia volucris. The two chalcones and the phenanthrene derivative were characterized as 2-propene-1-one-1-(2′,4′-dihydroxy-3′-methoxyphenyl)-3-(4″-methoxyphenyl) and 2-propene-1-one-1-(2′-hydroxy-4′-methoxyphenyl)-3-(4″-methoxyphenyl) and 6-hydroxy-2,4,7-trimethoxyphenanthrene(batatasin-I), respectively, by independent spectral analysis of the compounds and their acetyl derivatives. The structure of lusianin was established as 1-propanone-1-(2′,4′-dihydroxy-3′-methoxyphenyl)-3-(4″-methoxyphenyl) from spectral and chemical evidence. © 1995.

Chalcone and dihydrochalcone derivatives from the orchid Lusia volucris

Rotundatin, a new 9,10-dihydrophenanthrene derivative was isolated from the orchid, Dendrobium rotundatum, which also afforded the known stilbenoids 2,7-dihydroxy-3,4,6-trimethoxyphenanthrene, 2,7-dihydroxy-3,4,6-trimethoxy-9,10-dihydrophenanthrene, nudol, moscatin and batatasin-III. Rotundatin was shown to be 2,5,9-trihydroxy-4-methoxy-9,10-dihydrophenanthrene from spectral and chemical evidence. © 1992.

Rotundatin, a new 9,10-didydrophenanthrene derivative from Dendrobium rotundatum

Isoflaccidinin and isooxoflaccidin, new phenanthropyrone derivatives, isolated from the orchid Coelogyne flaccida were shown to be 2,7-dihydroxy-6-methoxy-5H-phenanthro [4,5-bcd] pyran-5-one and 2,7-dihydroxy-6-methoxy-9,10-dihydro-5H-phenanthro [4,5-bcd] pyron-5-one, respectively, from spectral and chemical evidence. © 1992.

Journal	Data powered by TypesetPhytochemistry
Publisher	Data powered by TypesetPERGAMON-ELSEVIER SCIENCE LTD
ISSN	0031-9422
Open Access	No