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- Two novel alkaloids from american ladybug Hippodamia-convergens (coleoptera, coccinellidae)Publication . Tursch, B.; Daloze, D.; Pasteels, J. M.; Cravador, A.; Braekman, J. C.; Hootele, C.; Zimmermann, D.During our continuing investigation of Coccinellidae alkaloids [l, 2,3] about 20,000 specimens of Hippodamia convergens were collected in Central California in September 1971. Fractionation of the methanolic extract by solvent partitions and repeated column chromatography afforded two novel alkaloids, hippodamin (I) and convergin (11) in a ratio of about 1 : 2.
- Chemical ecology of arthropods. 9. Structure and absolute configuration of hippodamine and convergine, two novel alkaloids from american ladybug hippodamia convergens (coleoptera- coccinellidae)Publication . Tursch, B.; Daloze, D.; Braekman, J. C.; Hootele, C.; Cravador, A.; Losman, D.; Karlsson, R.In a previous communication (2) the isolation of two defensive alkaloid, hippodamine and convergine, from the American ladybug Hippodamia convergens was reported. A preliminary chemical study (2) led to the hypothesis that hippodamine could be represented by (1), with unknown stereochemistry at carbon atom 2. Convergine was supposed to be a 3a or 6a hydroxyhippodamine.
- Acidite relative des groupes methyle de la 2,4,6- collidine dans le systeme phenyllithium solvants etheresPublication . Cravador, A.La position de la métallation de la 2,4,6- collidine est fonction des conditions expérimentales notamment de la nature de la base, du rapport molaire collidine-base et du solvant.
- Cleavage (deprotection) of selenoacetals to carbonyl compoundes: a comparative studyPublication . Burton, A.; Hevesi, L.; Dumont, W.; Cravador, A.; Krief, A.Phenyl and methyls (1) have found increasing interest in organic synthesis. They have been prepared from aldehydes or ketones (2) and selenols, from 1,1-bis(phenylseleno)-alkanes, and from 1,1,1-tris(seleno)-alkanes (5).
- 1,1-Bis(Phenylseleno)-and 1,1-Bis(Methylseleno)- alkyllithiums as building-blocks in organic synthesisPublication . Vanende, D.; Cravador, A.; Krief, A.1,1 - Bis(phenylseleno)alkyllithiums are conveniently prepared from the corresponding selenoacetals and lithium tetramethylpiperidide in HMPT/THF.
- Nouvelles méthodes de synthèse des méthylsélénoacétals et cétalsPublication . Cravador, A.Les bis (méthylséléno) acétals et cétals sont facilement accessibles à partir de dérivés carbonylés et de méthyltriméthylsilylséléniure ou de tris (méthylséléno) borane.
- Reduction vs acetalisation of some carbonyl-compounds by means of methylselenol and lewis-acidsPublication . Cravador, A.; Krief, A.; Hevesi, L.Aliphatic ketones and aromatic carbonyl compounds on reaction with methylselenol :and a Lewis acid, are shown to undergo acetalisation and/or reduction to methyl selenide, the unexpected reduction reaction being predominant in most cases.
- Nouvelles méthodes de synthèse utilisant une entité séléniée comme précurseur de fonctionPublication . Cravador, A.Nous sommes intéressés au cours des derniéres annés à la mise au point de schémas de synthèses utilisant une entité séléniée comme précurseur de fonction.
- Unexpectedly easy formation of alpha-seleno-carbonyl compounds from vinyl selenidesPublication . Cravador, A.; Krief, A.Seleno-carbonyl compounds are formed on reaction of seleninic acid or anhydride with vinyl selenides and vinyl sulphides.
- Unusual reactivity of selenoboranes towards epoxides: New selective routes to beta- hydroxyselenides and allylalcoholsPublication . Cravador, A.; Krief, A.Selenoboranes react with terminal, α, β-di- and trisubstituted epoxides to produce β-hydroxyselenides (or olefins) in the two first cases and allyl alcohols in the last one. A very high stereodescrimination has been observed for α, β-bisubstituted epoxides: the cis epoxide being much more reactive.