J. L. López-Pérez

Unambiguous configurational and conformational determination of thuriferic acid

Abstract The stereochemistry of thuriferic acid has been checked on the basis of spectral, chemical and molecular modelling findings. Under basic catalysis, the carbon alfa to the lactone carbonyl group in podophyllotoxone must be inverted instead of the carbon alfa to the ketone group, before the β-elimination, to give thuriferic acid.

The stereochemistry of thuriferic and epithuriferic acids

Abstract A new lignan, epithuriferic acid has been prepared from isopicropodophyllone. Its stereochemistry has been established on the basis of spectral, chemical and molecular modelling findings and compared to that of its 8′ epimer thuriferic acid, isolated from the Juniperus thurifera leaves.

A role for dipole moment in the activity of cyclolignans

Abstract The reactivity of podophyllotoxin and several related cyclolignans with different aminoderivatives has been checked with the aim of achieving a better understanding of their physico-chemical properties and of relating them to their pharmacological behaviour. Molecular modelling studies have shown that the relative orientation of the dipole moment in these cyclolignans might be directing the attack of these nucleophiles in the biosubstrate to different positions. These results also provide insights into the structure–activity relationships and further support for the recently proposed biological mechanism of cyclolignans.

A new coumarin from the fruits of Coutarea hexandra

A new 5-O-β-D-glucopyranosyl-4-(4-hydroxyphenyl)-7-methoxy-2H-chromen-2-one (1), together with four known compounds, one coumarin, 5-O-β-D-galactopyranosyl-4-(4-hydroxyphenyl)-7-methoxy-2H-chromen-2-one (2) and three cucurbitacins, 23,24-dihydrocucurbitacin F (3), 23,24-dihydro-25-acetylcucurbitacin F (4) and 2-O-β-D-glucopyranosyl-23,24-dihydrocucurbitacin F (5) have been isolated and characterised from the ethanol extract of Coutarea hexandra fruits. Their structures have been established by spectroscopic analysis (NMR and MS). Interpretation of the HMQC, HMBC, COSY-45 and NOESY experiments permitted us to establish stereochemistry of the natural products. All compounds were tested in cytotoxicity assays against the breast (MCF-7), lung (H-460), and central nervous system (SF-268) human cancer cell lines.

A new cucurbitacin glycoside from Kageneckia oblonga (Rosaceae).

Abstract A novel cucurbitacin glycoside has been isolated from aerial parts of Kageneckia oblonga R. et P. and shown to be 3β-(β-D-glucosyloxy)-16α,23α-epoxycucurbita-5,24-dien-11-one. The structure was established by usual spectroscopic and two-dimensional (2D ) NMR techniques. This compound has found to be nontoxic when tested in-vivo cell culture assays. In previous investigations we reported 23,24-dihydrocucurbitacin F and prunasine. This was the first report on cucurbitacins from the genus Kageneckia (Rosaceae).