Daniel Danion

Stereoselective, nonracemic synthesis of ω-borono-α-amino acids

Abstract ω-Unsaturated α-amino acids are synthesized through condensation of allyl and propargyl bromides or of 9-bromoundecene with a Ni(II) complex of the Schiff base derived from glycine and BPB. Hydroboration with Ipc 2 BH followed by oxidation with acetaldehyde affords enantiomerically pure ω-borono-α-aminocarboxylic acids.

Belokon's Ni(II) complex as a chiral masked glycine for the diastereoselective synthesis of 2-substituted 1-aminocyclopropane carboxylic acids☆

Abstract (1S,2R)- and (1R,2S)-Allonorcoronamic acids have been efficiently synthesised from the cyclic sulfate of 1,2-propanediol and Belokons complex (a complex of Ni(II) with glycine-(S)-2-[N′-(N-benzylprolyl)amino]benzophenone Schiff base ligands). The stereochemical outcome of the reaction was totally controlled by the sulfate partner.

Synthesis and reactivity of protected β-bromo α-iminoacids ; a convenient route to structurally diversified aminoacids

Abstract The title compounds are obtained by N-bromosuccinimide oxidation of protected didehydroaminoacids. Additions to the imino group are readily performed with borohydride, Grignard reagents or other nucleophiles. Heterocyclic aminoacids are available by subsequent displacement of bromine.

Hydroboration of vinylglycine and allylglycine as a route to boron-derivatives of α-amino acids

Abstract The hydroboration of protected vinylglycine and allylglycine with dicyclohexyl- or diisopinocampheylborane occurs chimio- and regioselectively with attachment of boron to the less substituted end of the carbon-carbon double bond. Homoserine or δ-hydroxynorvaline are readily obtained by H 2 O 2 CH 3 CO 2 Na oxidation of dicyclohexylborane derivatives and 2-amino-4-boronobutanoic acid or 2-amino-5-boronopentanoic acid by reaction of diisopinocampheylborane derivatives with excess of ethanal and deprotection.

Synthese et reactivite du diazoethylidene cyanacetate d'ethyle: Preparation de cyclopropene et de bicyclobutane gem-diactives.

Resume Ethyl chloromethylidenecyanoacetate, a synthetic equivalent of carbonyl chloride, reacts readily with diazomethane, under the conditions of the Arndt-Eistert synthesis of diazoketones, leading to ethyl diazoethylidenecyanoacetate. This diazocompound is a useful synthon which opens new routes to heterocycles or to small strained rings as cyclopropenes or bicyclobutanes.

Etude de cycloadditions aux allenes gem-diactives par deux groupes electroattracteurs

Resume Les allenes actives par deux groupes electroattracteurs gemines ont une reactivite tres proche de celle des cetenes et peuvent etre utilises comme equivalents synthetiques de ces composes. Plusieurs approches de ces alienes sont envisagees : reactions de dehydrohalogenation, ou transpositions analogues a la reaction de Wolff des diazocetones. Les cycloadditions aux imines ou aux diazoalcanes permettent un acces facile a des equivalents de β-lactames ou de cyclobutanones.

Hydroboration of methyl 2-acetamidoacrylate. Characterisation and nucleophilic reactivity of the resulting oxytriorganoborate

Abstract Hydroboration of methyl 2-acetamidoacrylate with dicyclohexylborane places boron exclusively at the 2-position. The product is obtained as an internal complex whose zwitterionic structure is established by X-ray cristallography. Alkali metal salts of this heterocyclic oxytriorganoborate are readily alkylated or acylated.

HYDROBORATION OF METHYL 2-ACETAMIDOACRYLATE. II: NEW ASPECTS OF THE REACTIVITY OF THE RESULTING OXYTRIORGANOBORATES

Abstract The heterocyclic borate complex obtained by hydroboration of methyl 2-acetamidoacrylate acts as an ambident nucleophile, affording N- or C-alkyl or acylalaninates according to experimental conditions. Mechanistic hypotheses are proposed to rationalize these results.

SUZUKI CROSS-COUPLING REACTIONS OF NONRACEMIC VINYLBORONO-α-AMINO ACIDS

Vinylborono-α-amino acids undergo Suzuki coupling with vinylic or aromatic halides, allowing an easy access to stereodefined unsaturated nonproteinogenic α-amino acids. With cesium fluoride as the base, the protective groups are not affected.

Oxidative ring opening of 2-pyrazolines. Application to lactamisation and formylation of 1,3-6h-thiazines.

Abstract Benzeneseleninic anhydride allows oxidative ring opening of 2-pyrazolines to α,β-unsaturated carbonyl compounds. Thus, a pyrazoline ring may be used as a masking, a stereodirecting and a latent formyl group in the synthesis of 7-amino 4-formyl cephem from 1,3-6H-thiazine.