Flavanthrin, the first dimeric 9,10-dihydrophenanthrene derivative, was isolated from the orchid Eria flava which also yielded the previously reported 9,10-dihydrophenanthrene coelonin (2a). The structure of flavanthrin was established as the 1.1'-dimer (1a) of its congener coelonin from spectral and chemical evidence. © 1988.

P L MAJUMDER

S BANERJEE

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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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

Structure of flavanthrin, the first dimeric 9,10-dihydrophenanthrene derivative from the orchid eria flava

Tetrahedron

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.

Phytochemistry

Phenanthrene derivatives from the orchid Coelogyne cristata

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.

Thunalbene, a stilbene derivative from the orchid Thunia alba

Callosumin, callosuminin and callosumidin, three new stilbenoids, were isolated from the orchid Agrostophyllum callosum which earlier afforded, besides 4-hydroxy-3,5-dimethoxybenzoic acid, 10 other structurally related stilbenoids, viz. orchinol, 6-methoxycoelonin, imbricatin, flaccidin, oxoflaccidin, isooxoflaccidin, flaccidinin, agrostophyllin, callosin and callosinin. The structures of callosumin, callosuminin and callosumidin were established as 2,4,6,7-tetramethoxy-9,10 dihydrophenanthrene, 2,4,6,7- tetramethoxyphenanthrene and 2,7-dihydroxy-5-ethoxy(ax)-6-methoxy-9,10- dihydro-5H-phenanthro[4,5-bcd]pyran, respectively, from spectral and chemical evidence. Although in naming callosumidin the systematic numbering system has been adopted, for ease of comparison of the spectral results the phenanthrene numbering system for the compound and its structural analogues is used.

Three stilbenoids from the orchid Agrostophyllum callosum

Callosin and callosinin, two new stilbenoids, were isolated from the orchid Agrostophyllum callosum, which also afforded, 4-hydroxy-3,5-dimethoxybenzoic acid, orchinol, 6-methoxycoelonin, imbricatin, flaccidin, oxoflaccidin, iso-oxoflaccidin, flaccidinin and agrostophyllin of previously known structures. Callosin was also isolated from another orchid, Coelogyne flaccida. The structures of callosin and callosinin were established as 2,6-dihyroxy-4,7-dimethoxy-9,10- dihydrophenanthrene and 2,6,7-trimethoxy-9,10-dihydro-5H-phenanthro [4,5-bcd]pyran-5-one, respectively, from spectral and chemical evidence. For ease of comparison of the spectral data the phenanthrene numbering system is used in this paper. © 1995.

Stilbenoids from the orchids Agrostophyllum callosum and Coelogyne flaccida

From the orchid, Arundina bambusifolia, were isolated two new stilbenoids, arundin and arundinin, besides p-hydroxybenzaldehyde, batatasin III, lusianthridin, flavanthrin, flavidin and the polyphenyl propanoid-malonate-derived compound 3,3′-dihydroxy-2,6-bis-(p-hydroxybenzyl)-5-methoxybibenzyl of previously known structures. Arundin and arundinin were shown to be 3-hydroxy-2,6-bis-(p-hydroxybenzyl)-5-methoxybibenzyl and 3,3′-dihydroxy-4-(p-hydroxybenzyl)-5-methoxybibenzyl, respectively, mainly from spectral evidence. © 1993.

Two stilbenoids from the orchid Arundina bambusifolia

An amorphous phenanthrene, named nudol has been isolated from Eulophia nuda, Eria carinata and E. stricta. It was identified as 2,7-dihydroxy-3,4-dimethoxyphenanthrene. Synthesis of nudol and its dimethyl ether is described. © 1985.

Journal	Tetrahedron
Publisher	-
ISSN	0040-4020