Lignans from the Seeds of Hernandia sonora.

The seeds of HERNANDIA SONORA L. (Hernandiaceae) yielded eight lignans. Five of them have already been described from other species of the HERNANDIA genus, namely podophyllotoxin ( 1), picropodophyllin ( 2), deoxypodophyllotoxin ( 3), hernandin ( 4), and podophyllotoxin acetate ( 5).

Fe(II)-induced reduction of labelled endoperoxides. NMR degradation studies on G3 factor and its methyl ether.

The behavior of G3 factor and of its methylated or fluorinated analogues G3Me and G3F, was studied under Fe(II) conditions. Degradation products were isolated and characterized in each case. The use of labelled compounds allowed us to propose mechanisms in which a tertiary radical is involved.

Alkylation of natural endoperoxide G3-factor. Synthesis and antimalarial activity studies.

Alkylation of the peroxyhemiketal function is described and all synthesised endoperoxides show good antimalarial activity. New rearrangement reactions in the presence of CsCO3, and preliminary results on Fe(II) chemical reduction of the O-O bond are presented.

Aggregation during coniferyl alcohol polymerization in pectin solution: a biomimetic approach of the first steps of lignification.

Coniferyl alcohol was polymerized in pectin solution in order to mimic the lignification that is the final step of biosynthesis of plant cell wall. Dehydrogenated polymers (DHP = coniferyl alcohol polymers = synthetic lignin) interact with pectin to form hydrophobic clusters as monitored by pyrene fluorescence spectroscopy. The structure of these clusters was studied during the polymerization of synthetic lignin by static and quasielastic light scattering and small angle neutron scattering experiments.

Stereoselective access to the versatile 4-aminohex-5-ene-1,2,3-triol pattern.

We developed a stereocontrolled route allowing potential access to the eight isomers of 4-benzylaminohex-5-ene-1,2,3-triol in two or four steps and ca. 50% yield from readily available chiral nonracemic cis- or trans-alpha,beta-epoxyimine precursors. A new (NH(4))(2)CO(3)-based carboxylation/intramolecular cyclization sequence allowed regio- and stereocontrolled C-3 epoxide opening while neat C-2 hydrolysis was ensured by simple aqueous acidic treatment.