L. Ramachandra Row

Novel hydroxy lignans from the heartwood of gmelina arborea

Abstract The structures of six new lignans isolated from the heartwood of Gmelina arborea have been determined. They are 6“ - bromo - isoarboreol, 4 - hydroxysesamin, 4,8 - dihydroxysesamin, 1,4 - dihydroxysesamin (gummadiol), 2 - piperonyl - 3 - hydroxymethyl - 4 - (α - hydroxy - 3,4 - methylenedioxybenzyl) - 4 - hydroxytetrahydrofuran, and the 4 - O - glucoside of 4 - epigummadiol. The 1 H and 13 C NMR and mass spectra of these compounds and their derivatives are discussed, and the structure previously assigned to a germination inhibitor from Aegilops ovata is questioned.

Phenolic constituents of Semecarpus anacardium

Abstract GLC-MS analysis of methylated bhilawanol from S. anacardium nuts and its oxidation product, the methyl ester of an aromatic carboxylic acid, conclusively proved that it contains more than seven closely related compounds. Two of them are major components which were isolated and shown to be 1-pentadec-Δ 5′ -enyl-2,3-dimethoxybenzene (I) and 1-pent biflavanoids A, B and C have been also isolated from defatted nuts of S. anacardium . The first of these has been characterized as its methyl ethers. A 1 and A 2 , for which biflavanone structures (VI) and (VII) are suggested on the basis of chemical and spectral evidence. The biflavanones B and C have been also characterized as their methyl ethers. Suggested structures are O -methyl derivatives of a IB-3′, IIA-8-binaringenin (XIV) for the former and IB-3′, IIA-8-biliquiritigenin (XV) for the latter.

New lignans from the heartwood of cleistanthus collinus

Abstract The isolation and characterisation of five new compounds and nine known compounds from the heartwood of Cleistanthus collinus are reported. The new compounds are wodeshiol 16 ,3,4-dihydrotaiwanin C 20 , and three new glycosides 24 , 25 and 26 of diphyllin and taiwanin E The 1 H and 13 C NMR spectra of these compounds are also reported.

New physalins from Physalis angulata and Physalis lancifolia. Structure and reactions of physalins D, I, G and K

Abstract The structures of physalins I, G and K are established respectively as 5,6-dihydro-5α-methoxy-6β-hydroxy, 4,5-dehydro-5,6-dihydro-4β-hydroxy and 5,6-dihydro-4α,5α-epoxy-6α-hydroxy derivatives of physalin B. The chemistry of physalin D, and the synthesis of physalins D and I from physalin F and physalin K from physalin G are described.

The structures of lignans from Gmelina arborea Linn

Five new lignans isolated from Gmelina arborea Linn have been characterised. The parent compound arboreol, is 2a,6e-dipiperonyl-1e,2e-dihydroxy-3,7-dioxabicyclo-[3,3,0]-octane. It is accompanied by its 2-O-methyl ether, the 2-O-ethyl ether and its 2-epimer, isoarboreol,. The fifth substance, gmelanone, is the first reported example of a lignan derived from 3,6-dioxabicyclo-[3,2,1]-octane.

The structure of Physalins F and J from Physalis angulata and P. Lancifolia

Abstract Physalins F and J are shown to be Physalin B 5β,6β-epoxide and 5α,6α-epoxide, respectively. The transformation of physalin F into physalin D (5,6-dihydro-5α,6β-dihydroxyphysalin B) and an acid-catalysed skeletal rearrangement of physalin F into isophysalin F are described.

Crystalline constituents of euphorbiaceae—XII: Isolation and structural elucidation of three new lignans from the leaves of Phyllanthus niruri Linn.

Abstract Three more new lignans from the hexane extract of Phyllanthus niruri Linn. are now reported besides phyllanthin and hypophyllanthin. The structure of niranthin is now established as 3,3′,4′,9,9′-pentamethoxy-4,5-methylenedioxy-8,8′-butyrolignan ( 2 ). Nirtetralin and phyltetralin are shown to be 1-phenyl tetralins. On the basis of NMR and mass spectra, nirtetralin is assigned the structure ( 7 ) and phyltetralin ( 11 ).

Physalins E and H, new physalins from Physalis angulata and P. lancifolia☆

Abstract From the stems and leaves of Physalis angulata and P. lancifolia, the isolation of five new physalins E, F, G, H and I is reported. The structures of physalins E and H are established respectively as 5,6-dihydro-5α,7α-dihydroxy and 7β-hydroxy derivatives of physalin B.

Crystalline constituents of euphorbiaceae—V: New lignans from Phyllanthus niruri Linn—The constitution of phyllanthin☆

Abstract An improved method for the isolation of phyllanthin and hypophyllanthin from the leaves of Phyllanthus niruri Linn. has been described. Their molecular formulae have been revised as C 24 H 34 O 6 and C 24 H 30 O 7 . The structure of phyllanthin is now shown to be (+)3,4,3′,4′,9,9′-hexamethoxy-8:8′-butyrolignan (IV) from its reactions and degradation to veratric acid. NMR spectra of phyllanthin and its derivatives support this structure.

Chemistry of terminalia species—VI : The constitution of tomentosic acid, a new triterpene carboxylic acid from terminalia tomentosa wight et arn

Abstract From the heartwood of T. tomentosa Wight et Arn, β-sitosterol, oleanolic acid (VI, R = R1 = H), arjunolic acid (I) and barringtogenol (IV) were isolated and in addition a new tetrahydroxy triterpene mono-carboxylic acid, now named Tomentosic acid. The triacetylmethyl tomentosate was oxidized to the corresponding ketone (XV) which could be reduced by forced Wolff-Kishner method to give methyl arjunolate (III). The above ketone also suffered isomerization in presence of alkali to give an α,β-unsaturated ketone (XVI). Further, during lactonization, the acid gives a trihydroxy anhydrolactone (X). The triacetylmethyl ester may be dehydrated using selenium dioxide to give methyldehydro arjunolate (XIX). From these reactions tomentosic acid is tentatively expressed as 2α,3β,19β,23-tetrahydroxy-olean-12-ene-28-oic acid (XII, R = H).