Agrostophyllin, a naturally occurring phenanthropyran derivative from Agrostophyllum khasiyanum

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

Abstract: 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.

[3,3]‐Sigmatropic Rearrangement Step in the Gold‐Catalyzed Cyclization of Allyl‐(ortho‐alkinylphenyl)methyl Ethers

Abstract: The gold-catalyzed conversion of allyl-(ortho-alkynylphenyl)methyl ethers was investigated, and allylated isochromenes were obtained. An optimization of the catalysis conditions with respect to different phosphane and carbene ligands on gold, different counterions, and different solvents was conducted. Subsequently, the scope and limitations of this reaction were investigated with 21 substrates. The mechanistic studies show an allylic inversion, as supported by NMR data and an X-ray crystal structure analysis, as well as an intermolecular reaction, as determined by crossover experiments. There is no competition of protodeauration even in the presence of water. All these observations differ from other related conversions and clearly indicate product formation by a [3,3]sigmatropic rearrangement in the step forming the new C-C bond.

Stilbenoids from the orchids Agrostophyllum callosum and Coelogyne flaccida

Abstract: 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-5 H -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.

Three stilbenoids from the orchid Agrostophyllum callosum

Abstract: Callosumin, callosuminin and callosumidin, three new stibenoids, 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.

Phenanthrene derivatives from the orchid Coelogyne cristata.

Abstract: 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.

13C NMR spectroscopy of neolignans

Abstract: The 13 C NMR spectra of 15 neolignans of several structural types and two lignans were analyzed and their carbon shifts assigned. The shifts of pyrogallol ether and ethyl phenyl carbinyl ether models were used in this connection. The stereochemistry of a dimeric sideproduct in the preparation of the latter models was determined by 13 C NMR analysis.

Moscatilin, a bibenzyl derivative from the orchid Dendrobium moscatum

Abstract: Moscatilin, a new bibenzyl derivative isolated from the orchid Dendrobium moscatum , was shown to have the structure 4,4′-dihydroxy-3,3′,5-trimethoxybibenzyl.

Nudol, a phenanthrene of the orchids Eulophia nuda, Eria carinata and Eria stricta

Abstract: 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.

Confusarin and confusaridin two phenanthrene derivatives of the orchid Eria Confusa

Abstract: From the orchid Eria confusa were isolated two new polyoxygenated phenanthrene derivatives, confusarin and confusaridin, which were shown to be 2,7-dihydroxy-3,4,8-trimethoxyphenanthrene and 2,6-dihydroxy-3,4,7,8-tetramethoxyphenanthrene, respectively.