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Janine Cossy

Publications and source records attributed to Janine Cossy.

At least 37 records · Page 2Linked to original sources
PubMed2004

Total synthesis of zincophorin and its methyl ester.

A total synthesis of the naturally occurring ionophore zincophorin has been realized. The route features an intramolecular oxymercuration of a cyclopropanemethanol and a Carroll-Claisen rearrangement for the respective elaboration of the C1-C12 and C13-C25 subunits, which have been assembled by using a highly diastereoselective titanium-mediated aldol condensation.

Anti-Bacterial Agents↗
PubMed2004

Total synthesis of natural (+)-(2's,3'r)-zoapatanol.

[reaction: see text] (+)-Zoapatanol was synthesized by using four key-steps: a Suzuki cross-coupling to prepare a (Z)-alpha,beta-unsaturated ester followed by an enantioselective dihydroxylation to control the C2' and C3' stereocenters, an intramolecular Horner-Wadsworth-Emmons olefination to construct the oxepane ring, and a chemoselective nucleophilic addition/Birch reduction process of a Weinreb amide to introduce simultaneously the beta,gamma-unsaturated ketone on the side-chain and regenerate alcohols from benzyl ethers.

Biological Factors↗
PubMed2003

Synthesis of the c14-c25 subunit of bafilomycin A1.

The enantioselective synthesis of the C14-C25 subunit of bafilomycin A1 was realized in a convergent route. The sequence involves two dynamic kinetic resolution steps of 2-alkyl 1,3-diketones that use optically active ruthenium complexes, an anti-selective reduction of a beta-hydroxyketone to control the C23 stereogenic center, and an aldol-type reaction under Evans' conditions, which sets the C17 and C18 stereogenic centers.

Ketones↗
PubMed2003

Total synthesis of zincophorin methyl ester.

[reaction: see text]. A convergent total synthesis of the methyl ester of zincophorin, an ionophore antibiotic, has been realized relying on a diastereoselective titanium-mediated aldol coupling between the C1-C12 and C13-C25 subunits. The latter fragment was prepared by using a Carroll-Claisen rearrangement.

Journal Article↗
PubMed2003

Total synthesis of (+)-strictifolione.

[reaction: see text] The synthesis of (+)-strictifolione was achieved from 3-phenylproprionaldehyde by using enantioselective allyltitanations to control the stereogenic centers at C6, C4', and C6' and a cross-methathesis to control the configuration of the double bond at C1'-C2'.

Aldehydes↗
PubMed2003

Tandem cross-metathesis/hydrogenation/cyclization reactions by using compatible catalysts.

[reaction: see text] A one-pot tandem cross-metathesis/hydrogenation/cyclization procedure was achieved at room temperature, under 1 atm of hydrogen, in the presence of a ruthenium catalyst and PtO(2) showing the compatibility of the two catalysts. This tandem reaction allows the synthesis of substituted lactones and lactols from acrylic acid and acrolein, respectively, in the presence of unsaturated alcohols.

Journal Article↗
PubMed2003

Stereoselective synthesis of polypropionate units and heterocyclic compounds by cyclopropylcarbinol ring-opening with mercury(II) salts.

The mercury(II)-mediated electrophilic ring-opening reaction of various cyclopropylcarbinol derivatives bearing adjacent stereocenters and a remote nucleophilic functional group provides a useful strategy for synthesizing compounds bearing several contiguous stereocenters. These highly diastereoselective reactions occur with anchimeric assistance by the internal nucleophilic moiety and afford synthetically valuable building blocks such as polypropionate units or heterocyclic compounds. The application of cyclopropylcarbinol ring-opening for the preparation of functionalized oxygen heterocycles in natural product synthesis is also outlined.

Journal Article↗
PubMed2002

Free-radical hydroxylation reactions of alkylboronates.

The radical hydroxylation of B-alkylcatecholboranes, easily prepared by hydroboration of olefins, has been investigated. When molecular oxygen was used as oxidizing agent, the corresponding alcohols were obtained directly without alkaline treatment. The presence of Lewis base additives such as Et3N or DABCO has a benefic effect on the selectivity and yield. Alternatively, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) reacts cleanly with B-alkylcatecholboranes to afford alkyl radicals that can be trapped by a second equivalent of TEMPO to give alkoxyamines. Reduction of the alkoxyamines with zinc in acetic acid affords the desired alcohols. The whole procedure is particularly mild and does not require any basic condition. The two approaches presented in this paper are valuable and represent mild alternatives to the classical alkaline oxidation of organoboranes to alcohols.

Journal Article↗
PubMed2002

Enantioselective allyltitanations and metathesis reactions. Application to the synthesis of piperidine alkaloids (+)-sedamine and (-)-prosophylline.

An enantioselective synthesis of the piperidine alkaloids (+)-sedamine and (-)-prosophylline is reported. The synthesis of (+)-sedamine has been achieved in 12 steps with an overall yield of 20% from benzaldehyde, and (-)-prosophylline was obtained in 15 steps with an overall yield of 9.2%, starting from D-glyceraldehyde acetonide 14. The key steps are enantioselective allyltitanation reactions and ring-closing or cross-metathesis reactions.

Alkaloids↗