Denyse Herlem

Oxydation photochimique D'amines tertiaires et D'alcaloïdes—VIII: Oxydation photochimique d'alcaloïdes indolinoindolizidiniques, vincadifformine, tabersonine, n(a)-acétyl dihydro-2,16 vincadifformine et n(a)-acétyl dihydro-2,16 tabersonine

Abstract Dye-sensitised photoxidation of the N b -nitrogen of indolino- indolizidine alkaloids, vincadifformine, tabersonine and their N a -acetyl-2-16-dihydro derivatives has been studied to determine the influence of structural factors on the site of oxidation.

Synthesis and structure-activity relationships of open D-ring galanthamine analogues

Open D-ring galanthamine analogues were prepared using ring-opening reactions of the quaternarized urethane or oxazolidine functions and were evaluated for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition potency.

Studies toward the total synthesis of polyoxygenated labdanes: preliminary approaches

Abstract Using the keto-ester 3 as a starting material, methods are developed for the successive introduction of hydroxy groups at C-6, C-7 and C-8 of a decalin system, as well as for elaboration of a C-9 pentadiene chain in a preliminary approach to the total synthesis of trihydroxylabdadienes.

Oxydation photochimique d'amines tertiaires et d'alcaloïdes—X : Introduction d'un groupement fonctionnel en α de l'azote nb de la yohimbine par oxydation photosensibilisee

Dye-sensitized photooxidation of the imino-ether 5, prepared from yohimbine 1a, led to the α-amino nitrile 9a when the reaction was performed in the presence of oxygen and KCN. Derivative 9a was hydrolyzed to the amide 9b, the transformation of which to carboxamido-5β-yohimbine 15 was studied.

Chemistry of larixol I- degradation of the side-chain and microbial hydroxylation

Abstract Degradation of the side-chain of larixol 1 , isolated from the turpentine oil of Larix sp. , led to ester 6 , useful intermediate for the synthesis of polyhydroxylated labdane diterpenes. Microbial hydroxylation of larixol and derivatives led to 2α-hydroxylated compounds which could be used for the hemisynthesis of forskolin type compounds.

Studies toward the total synthesis of diterpenes in the labdane series. III: Synthesis of two epimeric 6, 7, 8-trihydroxylabdadienes

Abstract The syntheses of 6β,7β, 8α, and 6β, 7β, 8β-trihydroxy labdadienes, 2a and 2b respectively, were performed starting from the decalin 3, in order to determine the exact structure of compounds, isolated from plant sources, for which configuration at C-8 was not clearly demonstrated. As a result, the structure 2a was established with certainty for crotomachlin, a diterpine from Croton macrostachys.

Chemistry of Larixol.II- Hemisynthesis of (−)-Borjatriol.

Starting from Larixol (1), the hemisynthesis of (−)-Borjatriol (2) has been realized. The key steps of this hemisynthesis were the introduction of hydroxyls at C(7), C(8), C(14) and C(15) starting from the mixture of epoxides 5 and 6.

Total synthesis of (±)-galanolactone

Abstract (±) - Galanolactone, 1 ,has been synthetised from the cyanoketone 2 prepared from geraniol.

Total synthesis of crotomachlin

Abstract The synthesis of the racemic 6β, 7β, 8α-trihydroxy labdadiene, 1 was achieved starting from decalin 3 . Diene 1 was found to be identical to crotomachlin, a diterpene from Croton macrostachys. in which the configuration at C-8 has not been established with certainty.