Edmundo A. Rúveda

13C NMR spectral analysis of lignans from Araucaria angustifolia

Abstract Pinoresinol dimethyl ether, secoisolariciresinol, lariciresinol, isolariciresinol and isolariciresinol-4′-methyl ether were isolated from the knots of dead trees of Araucaria angustifolia . The 13 C NMR spectra of these compounds, their methyl and acetyl derivatives, and the corresponding one of matairesinol, have been recorded and the signals assigned. On the basis of these assignments, the structure of the new monomethyl ether of isolariciresinol has been established.

Neolignans of Virola surinamensis

Abstract Elemicin, galbacin, veraguensin and two new neolignans, surinamensin and virolin, were isolated and characterized from the leaves of Virola surinamensis.

13C NMR spectral and conformational analysis of 8-O-4' neolignans

Abstract The 13C NMR spectra of the erythro and threo forms of representative members of the 8-O-4′ type of neolignans were recorded and the signals assigned. Based on these assignments and on the comparison with previously reported 1H NMR data, the most probable conformations for the above mentioned stereoisomers are suggested.

Lignans of Araucaria angustifolia and 13C NMR analysis of some phenyltetralin lignans

Abstract Secoisolariciresinol monomethyl ether and lariciresinol-4-methyl ether were isolated from the knots of dead trees of Araucaria angustifolia . On the basis of spectral evidence, the position of the OH group was located in these compounds. The 13 C NMR spectra of the phenyltetralin lignans galbulin, galcatin, isogalcatin and cyclogalgravin have also been recorded and the signals assigned, based on the methyl shifts of cyclogalgravin.

13C NMR analysis of aporphine alkaloids

Abstract The 13 C NMR spectra of some tertiary and quaternary aporphine alkaloids are recorded and the signals assigned. The substituent shielding effects together with the effects of N - and O -methylation, and the twisting of the biphenyl system, are analysed and utilized in the spectral interpretation.

10-epideoxycumambrin B and other constituents of Stevia yaconensis var. subeglandulosa

Abstract The aerial parts of Stevia yaconensis var. subeglandulosa afforded in addition to the known guaianolides ludartin and dehydroleucodin a new guaianolide 10-epi-8-deoxycumambrin B whose relative and absolute configurations were established by X-ray crystallography. Chemical transformations of ludartin established its relative and absolute stereochemistry.

Aristololactams of Aristolochia argentina

Abstract Four new lactams have been isolated and characterized from the roots of Aristolochia argentina .

13C NMR analysis of podophyllotoxin and some of its derivatives

Abstract The 13C NMR spectra of podophyllotoxin and some of its derivatives were recorded and the signals assigned. Based on these assignments and on comparison with previously reported 1H NMR data, information regarding the stereochemistry and conformations of the products under study was obtained.

13C NMR spectral analysis of some isoquinoline alkaloids

Abstract The 13C NMR spectra of some isoquinoline and tetrahydroisoquinoline alkaloids and their corresponding N-methosalts and of the bisbenzylisoquinoline alkaloid isochondodendrine were recorded and the signals assigned. The substituent shielding effects and the 13C1H long range couplings were analysed and utilized in the spectral interpretation.

Argentilactone, a novel 5- hydroxyacid lactone from Aristolochia argentina

Abstract Argentilactone, a new constituent of the rhizomes of Aristolochia argentina, was isolated and characterized as the (−)-(5R)-δ-lactone of 5-hydroxydodeca-Z,Z-2,6-dienoic acid.