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Nouvelles méthodes de synthèse utilisant une entité séléniée comme précurseur de fonction
No full textNous sommes intéressés au cours des derniéres annés à la mise au point de schémas de synthèses utilisant une entité séléniée comme précurseur de fonction
Cleavage (deprotection) of selenoacetals to carbonyl compoundes: a comparative study
No full textPhenyl 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 synthesis
No full text1,1 - Bis(phenylseleno)alkyllithiums are conveniently prepared from the corresponding selenoacetals and lithium tetramethylpiperidide in HMPT/THF
Nouvelles méthodes de synthèse des méthylsélénoacétals et cétals
No full textLes bis (méthylséléno) acétals et cétals sont facilement accessibles à partir de dérivés carbonylés et de méthyltriméthylsilylséléniure ou de tris (méthylséléno) borane
Acidite relative des groupes methyle de la 2,4,6- collidine dans le systeme phenyllithium solvants etheres
No full textLa 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
Chemical ecology of arthropods. 9. Structure and absolute configuration of hippodamine and convergine, two novel alkaloids from american ladybug hippodamia convergens (coleoptera- coccinellidae)
No full textIn 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
Two novel alkaloids from american ladybug Hippodamia-convergens (coleoptera, coccinellidae)
No full textDuring 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