RESUMO
NMR studies have shown that seven new sesquiterpenoids, 3, 4, 5a, and 7-10, isolated from dried samples of the New Zealand liverwort Lepidolaena hodgsoniae have the same substituted cyclopentapyran ring system as the previously described insecticidal sesquiterpene diene hodgsonox (1), which has been reported only from this plant. In all but one compound, 10, the 1,1-disubstituted double bond of hodgsonox has migrated into an endocyclic position, but only two, 5a and 9, have the double bonds in conjugation. These seven new compounds represent a variety of different oxidation levels. Two of the new derivatives, 9 and 10, were isolated only from an aged sample and are presumably artifacts. The only other terpenoid isolated in significant quantity was (7R,10R)-calamenene (2).
Assuntos
Hepatófitas/química , Inseticidas/isolamento & purificação , Plantas Medicinais/química , Piranos/isolamento & purificação , Sesquiterpenos/isolamento & purificação , Compostos de Vinila/isolamento & purificação , Inseticidas/química , Inseticidas/farmacologia , Conformação Molecular , Estrutura Molecular , Nova Zelândia , Ressonância Magnética Nuclear Biomolecular , Sesquiterpenos Policíclicos , Piranos/química , Piranos/farmacologia , Sesquiterpenos/química , Sesquiterpenos/farmacologia , Estereoisomerismo , Terpenos/química , Terpenos/isolamento & purificação , Compostos de Vinila/química , Compostos de Vinila/farmacologiaRESUMO
[structure: see text] The synthesis of some simple compounds containing the previously unreported 3-methylene-2-vinyltetrahydropyran system, a unique feature of the liverwort metabolite, hodgsonox is reported. Key features are the creation of an acrolein substituted in the alpha-position with a three-carbon chain bearing a terminal electrophilic site, addition of a vinyl group, and cyclization.
Assuntos
Piranos/química , Piranos/síntese química , Compostos de Vinila/química , Espectroscopia de Ressonância Magnética , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria UltravioletaRESUMO
Several Anisotome diterpene derivatives were synthesized in an attempt to obtain a crystalline compound for X-ray analysis. Although we were unable to obtain a suitable crystal, the absolute configuration of the irregular diterpene skeleton was determined using two other techniques: a circular dichroism (CD) protocol based on a tetraarylporphyrin molecular tweezer that allowed prediction of the absolute stereochemistry on a microscale level, and a method employing differences in NMR shifts from derivatization of the naturally occurring acid 1 with enantiomers of a phenylglycine methyl ester (PGME) chiral anisotropic reagent. The excellent agreement between the CD and NMR methods led to the assignment of a 2S-absolute configuration for anisotomenoic acid 1.
Assuntos
Dicroísmo Circular , Diterpenos/química , Glicina/análogos & derivados , Espectroscopia de Ressonância Magnética , Magnoliopsida/química , Glicina/síntese química , Glicina/química , Modelos Moleculares , Conformação Molecular , Estrutura Molecular , Espectrofotometria Ultravioleta , EstereoisomerismoRESUMO
The incorporation of [1-13C] labelled glucose into hodgsonox, a sesquiterpene epoxide with a unique, doubly allylic ether functionality has been studied in axenic cultures of the liverwort Lepidolaena hodgsoniae. Quantitative 13C NMR spectroscopic analysis showed that the isoprene units are derived exclusively from the methylerythritol phosphate pathway.
