V. Speziale

Optimization of the enzymatic synthesis of amino acid esters. Reaction in polyphasic medium

Abstract N-acetyl-L-Tyrosine Ethyl Ester (ATEE) was synthesized from N-acetyl- l -Tyrosine and ethanol, with immobilized chymotrypsin as catalyst. For this purpose, a biphasic liquid reaction mixture consisting of an organic chloroform phase and an aqueous phase was used. This system allows the shift of the reaction equilibrium towards ATEE synthesis by achieving continuous ATEE extraction in the organic phase. Synthesis rates of up to 90% were obtained by optimizing the reaction conditions and controlling the pH of the aqueous phase.

PREPARATION OF A NEW SERIES, THE 3-UREIDOMETHYLENECOUMARINS BY CONDENSATION OF 4-HYDROXYCOUMARIN WITH SUBSTITUTED UREAS

We report the synthesis in high yield of a series of 3-ureido-methylenecoumarins by condensation of substituted ureas with 4-hydroxycoumarin in the presence of ethyl orthoformate.

Reaction of 4-Hydroxy-6-Methyl-3-β-arylpropionyl-2-Pyrones with Phenylhydrazine-Synthesis of a New Pyrazole Series

Abstract We report the synthesis of a new pyrazole series by the action of phenylhydrazine on 4-hydroxy-6-methyl-3-β-arylpropionyl-2-pyrones.

Hydroboration d'amines insaturees—IV : Hydroboration-alkylation de propargylamines par des dialkylboranes mixtes

Resume Hydroboration-alkylation of substituted or unsubstituted propargylamines with thexylalkylboranes rapidly gives good yields of ethylenic amines. A tendency towards rearranged products depends on the basicity of the starting acetylenic amines. Comparatively to corresponding alkynes, acetylenic amines are characterized—by anomalous regioselectivity of the hydroboration, and—by anomalous migratory aptitudes of thexyl and alkyl groups, depending on the amine basicity and modified by addition of trimethylamine oxide.

Hydroboration d'amines insaturees—II: Régio et stéréosélectivité de l'hydroboration-alkylation d'amines acétyléniques

Abstract The hydroboration reaction of acetylenic amines R 1 R 2 NCH(R 3 )CCR 4 was studied. We report the first results of a study of the reactivity of dialkylborane R 2 BH towards these amines which allow us to propose a new method for the synthesis of differently substituted β-ethylenic amines. The regioselectivity and the stereoselectivity of this reaction are examined and allow us to set out the possibility of a trans hydroboration.

Hydroboration d'amines insaturees: IX. Role d'une liaison PIV-N sur la complexation azote—bore lors de la reaction d'hydroboration d'amines N-allyliques

Abstract The amino group of N -allylic amines which is protected by a phosphorylated grouping hinders nitrogen—boron coordination and allows normal addition of the boron hydrides. The hydroboration—oxydation reaction of phosphorated N -allylic amines, by appropriate hydroboration agents, lead to N -phosphorated 3-aminopropanols with very good yields.

Synthesis of 4-Hydroxy 6-Methyl 3-β-Arylpropionyl 2-Pyrones by Selective Catalytic Hydrogenation of 3-Cinnamoyl 4-Hydroxy 6-Methyl 2-Pyrones

Abstract We report a simple method for synthesis of 4-hydroxy 6-methyl 3-β-arylpropionyl 2-pyrones 1 from 3-cinnamoyl 4-hydroxy 6-methyl 2-pyrones by selective hydrogenation at ambient temperature under pressure using 10% palladium on carbon as catalyst.

Hydroboration d'amines insaturees: XI. Regio- et stereoselectivite des hydrures du bore vis a vis d'amines propargyliques N-phosphorylees

Abstract The regioselectivity and the stereoselectivity of the hydroboration of N -alkylallylphosphoramide was examined. This study shows the preferential formation of γ-boron derivatives (90 to 100%) and the excellent stereospecificity of the reaction (100% ( Z ) configuration). The P IV -N bond hinders the nitrogen-boron coordination which is responsible for the anomalous behavior of N -propargylic amines towards hydroboration and allows the same regio- and stereo-selectivity as for alkynes. The iodination of boron derivatives leads, with good yields, to N -phosphoryl-β-ethylenic amines.

Hydroboration of Unsaturated Amines VIII A Convenient Synthesis of Amino-3 Propanol-1

Abstract A new route with increased yield and stereoselectivity is reported for the synthesis of amino-3 propanols-1. It involved a hydroboration-oxidation reaction using bora- 9 bicyclo |3, 3, 1| nonane. The amino group was protected by a phosphorylated grouping giving rise to novel and potentially useful phosphorylated reagents.

Hydroboration d'amines insaturees: VII. Stereochimie et mecanisme

Abstract Hydroboration and iodination of acetylenic and brominated acetylenic amines, give ethylenic amines in which the double bond is demonstrated by the formation of trans -substituted equivalent boranes. Taking advantage of regioselective and stereoselective results, thermodynamic control is assumed. A kinetic study of the evolution of the reaction products confirms this hypothesis.