"Reaction between N-alkylhydroxilamines and chiral enoate esters: More experimental evidence for a cycloadition-like process, a rationale based on DFT theoretical calculations, and stereoseletive synthesis of new enantiopure b-amino acids

". ALBERTINA MOGLIONI, ELENA MURAY, JOSÉ CASTILLO, ÁNGEL ÁLVAREZ-LARENA, GRACIELA MOLTRASIO, VICENÇ BRANCHADELL AND ROSA ORTUÑO

JOURNAL OF ORGANIC CHEMISTRY

AMER CHEMICAL SOC

Año: 2002 vol. 67 p. 2402 - 2410

0022-3263

The reactions between N-benzyl- and N-methylhydroxylamine and chiral enoate esters, derivedfrom D-glyceraldehyde and (-)-verbenone, respectively, have been investigated. Theoreticalcalculations show that the most favorable mechanism involves the concerted cycloaddition of thehydroxylamine to the substrate. This result is in good agreement with the stereospecificity observed when the trisubstituted olefins are used. The open-chain adducts have been isolated when the processes are carried out at low temperatures and for short reaction times. These compounds evolve to the corresponding isoxazolidinones on standing at room temperature or under acid catalysis.The high ð-facial diastereoselection has been rationalized on the basis of steric effects induced bythe dioxolane ring for D-glyceraldehyde derivatives or by the cyclobutane gem-dimethyl substitution for esters prepared from (-)-verbenone. As an application of these reactions, new â-amino acids have been synthesized in a highly efficient and stereocontrolled manner.