Siméon Arseniyadis

Cyclisation d'amines γ et δ-alleniques. Synthese d'alcenyl-2 pyrrolidines et d'alcenyl-2 piperidines.

Abstract The entitled heterocyclic compounds can be obtained with good yields and exclusively with E configuration by the respective cyclisation of secondary γ-allenic and δ-allenic amines promoted by silver nitrate or by mercuric chloride. In the second case, the reaction has to be followed by demercuration in phase transfer conditions.

Asymmetric synthesis: XII:Stereocontrolled electrophilic-nucleophilic α,α'-substitution of the pyrrolidine ring

Abstract The synthesis of 2-cyano-5-oxazolopyrrolidine 3 , a chiral pyrrolidine synthon, is described. Conditions were established that permitted sequential chemoselective reactions at the C-2 aminonitrile (electrophilic substitution) and at the C-5 aminoether (nucleophilic substitution) centres of 3 . A stereospecific decyanation of the alkylated aminonitrile allowed the formation of the first asymmetric centre at C-2 of the pyrrolidine ring. The first enantioselective synthesis of (+)-(S)-trans-2-heptyl-5-ethyl-pyrrolidine 9 , a component of the venom of the ant Solenopsis punctaticeps served as an example of the method. Both enantiomers of cis-2-heptyl-5-ethyl pyrrolidine 13 were obtained from the minor diastereomers 7 and 8 which were formed on reaction of oxazolidines 5a and 5b with Grignard reagents. The stereochemical outcome of the substitution reactions is discussed. In addition, full data on the synthesis of ant venon alkaloid (+)- (S)-trans-2-heptyl-5-butyl-pyrrolidine and its cis stereomer are given.

Chemobiological transformations of octalone and hydrindenone derivatives

Abstract Examples are given for allylic hydroxylations with Rhizopus arrhizus ATCC 11145. Chemical allylic hydroxylations are compared with microbiological

ASYMMETRIC-SYNTHESIS X: A CHIRAL PYRROLIDINE SYNTHON FOR A NEW APPROACH TO THE SYNTHESIS OF ALKALOIDS

Abstract The synthesis of chiral 2-cyano-5-oxazolopyrrolidine 3 is reported. The synthesis of the optically pure ant venom alkolaid, (+)-(S)- trans -2-heptyl-5-butyl-pyrrolidine 7 , has been achieved from 3 .

Synthetic approaches to pentacyclic triterpenes of the arborane family

Abstract Synthesis, from 2-methylcyclohexane-13-dione and 2-methylcyclopentane-1,3-dione, of optically pure bicyclic intermediates representing the A/B and D/E fragments required for an approach to isoarborinol.

Asymmetric synthesis XIV: A short and efficient synthesis of 3,5-disubstituted pyrrolizidine alkaloids via the CN(R,S) method☆☆☆

Abstract The enantiospecific synthesis of the dextrorotatory enantiomer of the ant venom alkaloid 3-heptyl-5-methylpyrrolidine 11 has been achieved in four steps and 31% overall yield from the chiral 2-cyano-5-oxazolopyrrolidine synthon 4 . On the basis of previous results it was concluded that the absolute configuration of + 11 is 3S, 5R, 8S in disagreement with an earlier report.

ACHILLEOL B : A NEW TRICYCLIC TRITERPENE SKELETON FROM ACHILLEA ODORATA L.

A new triterpene 1a from Achillea odorata L. has been isolated, and its structure established on the basis of its spectroscopic properties as well as those of its acetylderivative 1b. 1a shows the first example of monocyclic triterpene skeleton, biosynthetized in the first step of cyclization of squalene oxyde.

Left and right-half taxoid building blocks from (S)-(+)-Hajos-Parrish ketone

Abstract An efficient 11-step synthesis of the optically homogeneous bridged ring system 4 , and a 5-step synthesis of the cyclohexane derivative 5a from Hajos-Parrish ketone is presented.

Asymmetric synthesis. XIII: Synthesis of 2-alkylpyrrolidines: towards azabicyclic systems

Abstract The enantiospecific synthesis of a series of 2(S)-alkylpyrrolidines from 2-cyano oxazolopyrrolidine synthon 1 is described. Two of the synthesised compounds represent key intermediates towards ozabicyclic alkaloids.

Studies towards the total synthesis of taxoids. A straightforward procedure for the taxoid BC substructure

Abstract The aldol condensation of the ketone 6 and the aldehyde 7 followed by an annelation-fragmentation afforded the bicyclo[6.4.0]dodecane derivative 3 with the appropriate functionalities for further elaboration.