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Studies of the dichloromethane extract of stems and the methanolic extract of fruits of Piper wightii Miq. resulted in the isolation of 12 compounds, all new for this species. They comprise a novel neolignan 1, a neolignan new as a natural product 2, a novel cyclohexane 5, two known neolignans 3 and 4, one known cyclohexane 6, and six known alkaloids 7, 8, 9, 10, 11 and 12.

A Study of Nuclear p-Anisylation of 2, 4-Dihydroxydesoxybenzoin, 5, 7-Dihydroxyisoflavone and 5, 7-Dihydroxychromone

The secondary metabolites isolated from Piper species for the period 1907 to June 1996 have been reviewed. Nearly six hundred chemical constituents belonging to different classes of bioactive compounds are listed together with their source(s) and references. © 1997 Elsevier Science Ltd

Four new compounds, a lignan and three neolignans, together with one known neolignan have been isolated from the leaves and stems of Piper clarkii . Their structures were established on the basis of 1 H, 13 C and 1 H 1 H COSY NMR, NOE and mass spectral data and CD curves. The novel lignan was identified as (2 S ,5 S )-diveratryl-(3 R ,4 S )-dimethyltetrahdrofuran. The structures of the new neolignans were established as (7 R ,8 R ,1′ S )- Δ 8′ -1′-methoxy-3,4-methylenedioxy-1′,6′-dihydro-6′-oxo-7.0.4′,8.3′-lignan[2 R ,3 R ,5 S )-2-(1,3-benzodioxol-5-yl)-3,5-dihydro-5-methoxy-3-methyl-5-(2-propenyl)-6(2H)-benzofuranone], (7 S ,8 S ,3′ R )- Δ 8′ -3,3′,4-trimethoxy-3′,6′-dihydro-6′-oxo-7.0.4′,8.3′-lignan[2 S ,3 S ,3 aR )-2-(3,4-dimethoxyphenyl)-3,3a-dihydro-3a-methoxy-3-methyl-5-(2-propenyl)-6(2H)-benzo-furanone] and rel-(7 S ,8 S ,1′ R ,3′ R )- Δ 8′ -5′-methoxy-3,4-methylenedioxy-1′,2′,3′,4′-tetrahydro-2′,4′-dioxo-7.3′,8.1′- lignan[(7 S ,6 S ,5 R ,1 R )-7-(1,3-benzodioxol-5-yl)-3-methoxy-6-methyl-5-(2-propenyl)bicyclo[3.2.1]oct-3-ene-2,8-dione]. The known neolignan has been identified as denudatin B.

A new benzoic acid ester, 2-E-[2″-oxo-cyclopent-3″-en-1″-ylidene]ethyl benzoate, together with tritriacontane, tetratriacontanol and β-sitosterol have been isolated from a petrol extract of the leaves of Uvaria narum. The structure of the new ester has been established on the basis of spectral data and finally confirmed by X-ray crystallography. Glut-5(6)-en-3-ol and betulapren-11-ol have also been isolated from a petrol extract of the leaves and stems of U. hookeri; this is the first report of the isolation of the latter compound from the genus Uvaria.

Department of Chemistry, University of Delhi, Delhi-11 0 007, India Tyagi, 0. D., Prasad, A. K., Wengel, J., Boll, P.M., Olsen, C. E., Parmar, V. S., Sharma, N. K., Jha, A. and Bisht, K. S., 1995. Neolignans from Piper schmidtii and Reassignment of the Structure of Schmiditin. - Acta Chern. Scand. 49: 142 -148 © Acta Chemica Scandinavica 1995. A new neolignan, (7R,8S,1 'S)-A

The stems and leaves of Piper clarkii have yielded two new neolignans [nomenclature follows Gottlieb, O. R. (1978) Prog. Chem. Org. Nat. Prod. 35 , 1], rel-(7R,8R,1′S,3Ŕ,4′S)-Δ 8′ -1′,2′,3′,4′-tetrahydro-4′-hydroxy-5′- methoxy-3,4-methylenedioxy-2′-oxo-7.3′,8. 1′-lignan (clarkinol) and (7R,8R, 1′S)-Δ 8′ - 1′,6′-dihydro- 1′,3,4-trimethoxy-6′- oxo-7.0.4′,8.3′-lignan, as well as the new isoprenylated phenol, 2-(3-methyl-2-butenyl)-3,4,5-trimethoxyphenol. In addition, velutin (3′,7-dimethoxy-4′,5-dihydroxyflavone) and a known neolignan (7R,8S,l′S)-Δ 8′ -1′,4′-dihydro-5′- methoxy-3,4-methylenedioxy-4′-oxo-8. 1′,7.0.2′-lignan, are reported and the 1 H NMR data of the latter are reassigned.

Two new neolignans, (7R,8R,3′R)-7-acetoxy-3′,4′-dimethoxy-3,4-methylenedioxy-6′-oxo-Δ-1′,4′,8′-8.3′-lignan (1) and (7R,8R,3′R)-7-hydroxy-3′,4′-dimethoxy-3,4-methylenedioxy-6′-oxo-Δ-1′,4′,8′-8.3′-lignan (2) were isolated from the petroleum ether extract of stems of Piper wightii Miq. The structure were elucidated on the basis of their spectroscopic analysis and chemical transformation. Additionally five known neolignans, isodihydrofutoquinol A (3) and B (4), lancifolin C (5) and D (6) and wallichinine (7) and two known α,α'-diaryl-β,β'-dimethyltetrahydrobenzofuran lignans, calopiptin (8) and machilin G (9), were isolated for the first time from Piper wightii. The new neolignan 2, isodihydrofutoquinol B (4), lancifolin C (5) and wallichinine (7) were also isolated from the methanolic extract of fruits of the same species alongwith gelbelgin (10), also a known lignan of the tetrahydrobenzofuran type.

Studies of the petroleum ether extract of the stems of Piper wightii Miq. resulted in the isolation of three novel 2′-oxo-8.1′- and 4′-oxo-8.5′-neolignan with unusual structures, namely 4′,5′-dimethoxy-3,4-methylenedioxy-2′-oxo-Δ 3′,5′,8′ -8.1′-lignan (6-[2-(1,3-benzodioxol-5-yl)-1-methylethyl]-3,4-dimethoxy-6-(2-propenyl)-2,4-cyclohexadien-1-one) ( 1 ), iso -4′,5′-dimethoxy-3,4-methylenedioxy-2′-oxo-Δ 3′,5′,8′ -8.1′-lignan ( iso -6-[2-(1,3-benzodioxol-5-yl)-1-methylethyl]-3,4-dimethoxy-6-(2-propenyl)-2,4-cyclohexadien-1-one) ( 2 ) and 1′,2′-dimethoxy-3,4-methylenedioxy-4′-oxo-Δ 3′,5′,8′ -8.5′-lignan (2-[2-(1,3-benzodioxol-5-yl)-1-methylethyl]-4,5-dimethoxy-4-(2-propenyl)-2,5-cyclohexadien-1-one)( 3 ) together with one novel tetrahydrofuran lignan, rel-(7 S ,8 S ,7′ S ,8′ S )-3′,4′-dimethoxy-3,4-methylenedioxy-8.8′,7.O.7′-lignan (2 S ,3 S ,4 S ,5 S )-5-[5-(3,4-dimethoxyphenyl)-3,4-dimethyl-2-tetrahydrofuranyl]-1,3-benzodioxol) ( 4 ). The structures were elucidated on the basis of spectropic data ( 1 H-, 2D- and 13 C NMR, NOE, UV, IR and MS). Additionally,two known neolignans, rel-(7 S ,8 R ,3′ R ,1′ S )-3′,4′-dimethoxy-3,4-methylenedioxy-6′-oxo-Δ 4′,8′ -8.3′,7.O.2′-lignan (fargesone A, 5 ) and rel-(7 S ,8 R ,3′ R ,1′ R )-3′,4′-dimethoxy-3,4-methylenedioxy-6′-oxo-Δ 4′,8′ -8.3′,7.O.2′-lignan (fargesone B, 6 ) were isolated for the fist time from P. wightii .

Three and a half years ago the Danish International Development Agency agreed to finance a joint research programme between the Chemisay Departments of University of Delhi, India, and Odense University, Denmark. The grant was given as a result of a new policy after which the Agency would finance scientific education projects of potential benefit to a third world country and to a minor extent to Denmark. The title of the project is: "Isolation, structure elucidation and biological activity of potential insecticides from Piper species of importance in agriculture and rural development." The Danish producer of pesticides, Cheminova, Inc., generously agreed to carry out biological testing of plant extracts. Naturally occurring long-chain N-isobutylamides have long been recognized as a class in which insecticidal activity is common. As a specific example one can refer to the investigation of Miyakado et al. (15) for which an amide, pipercide, from black pepper, Piper nigrum, was more toxic against adzuki bean weevils than pellitorine and just as active as the pyrethroids.

The unknown enantiomeric lignan (−)-machilin G and the known lignans (+)-calopiptin, (−)-zuionin A as well as a new neolignan kadsurin A and known neolignans futoquinol, isodihydrofutoquinol A, isodihydrofutoquinol B, along with parsley apiole, have been isolated from the leaves and stem of Piper schmidtii . The unpublished 13 C NMR data of the above known neolignans and the reassignment of the 1 H NMR spectrum of isodihydrofutoquinol B are also reported.

Three biogenetically related compounds have been isolated from Agave americana L. namely 5-hydroxy-7-methoxy-2-tritriacontyl-4H-1-benzopyran-4-one, tetratriacontyl hexadecanoate and tetratriacontanol. Two of them exhibited significant antibacterial activity.

A new aristolactam, 10-amino-4-hydroxy-2,3-dimethoxyphenanthrene-1-carboxylic acid lactam, was isolated from the stem of Piper acutisleginum. The structures of two related alkaloids, piperolactam B and D, have been revised.

A novel type of wax ester has been isolated from a petrol extract of stems and leaves of Piper clarkii and its structure established as 3-(4-hydroxyphenyl)propyl tetracosanoate. The structure was verified by synthesis. The oxygenated cyclohexane (+)-crotepoxide and β-sitosterol were also isolated.

Regioselectivity has been observed in the deacetylation of peracetates of polyphenolic aromatic ketones by lipases from porcine pancreas (PPL) and Candida cyclindracea (CCL) suspended in organic solvents. The deacetylation of acetoxyl groups at positions para and meta to the carbonyl (ketonic) group is favoured over the one at the ortho position.

Two naturally occurring isoflavanones, viz. dihydrocladrin and homoferreirin, and related compounds, di-O-methylhomoferreirin and 7-O-methylsativanone, have been synthesized in racemic forms from the corresponding desoxybenzoins using the ethoxymethyl chloride method from the literature.