Asymmetric [3+2] cycloaddition reaction of a chiral cyclic nitrone for the synthesis of new tropane alkaloids

• Published in: Tetrahedron 2020-01, Vol.76 (1), p.130764, Article 130764
• Main Authors: Esteban, Alberto, Izquierdo, Ignacio, García, Nieves, Sexmero, María J., Garrido, Narciso M., Marcos, Isidro S., Sanz, Francisca, Jambrina, Pablo G., Ortega, Pablo, Diez, David
• Format: Article
• Language: English
• Subjects: 1,3-Dipolar cycloaddition; Isoxazolidines; Nitrones; Tropane alkaloids; α,β-Unsaturated lactones
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2019.130764

The 1,3-dipolar cycloaddition of a chiral nitrone with α,β-unsaturated lactones was carried out to give the corresponding isoxazolidines. Tetrahydro-1,3-oxazines with an oxa-tropane skeleton were obtained in one step by alkylation. The structures of several of these compounds were corroborated by X-ray diffraction and molecular modelling studies confirmed the results and proposed a mechanism for their formation. [Display omitted] •1,3-Dipolar cycloaddition of a chiral nitrone with α,β-unsaturated lactones was carried out to give the corresponding isoxazolidines.•Tetrahydro-1,3-oxazines with an oxa-tropane skeleton have been obtained in one step for the corresponding isoxazolidines.•A revised version of the proposed mechanism has been stablished using molecular modelling studies.•The structure of several of these compounds were corroborated by X-ray diffraction and NMR spectra has been completely stablished.