Stereoselective approach to hydroxyindolizidines: protection/deprotection of the nitrone functionality via cycloaddition/retrocycloaddition.
The enantiomerically pure indolizidine (-)-21 has been synthesized starting from L-malic acid. The key intermediate 20 has been assembled through an intramolecular 1,3-dipolar cycloaddition of a nitrone generated in situ by retrocycloaddition from isoxazolidine 17 or 18. The configuration of the new three stereocenters was set up with complete control in the cycloaddition step. The presented synthetic route provides a general and highly selective methodology toward indolizidines having the [1,8a]-cis configuration.
Cordero
F M
FM
Dipartimento di Chimica Organica "U. Schiff", Centro di Studio sulla Chimica e la Struttura dei Composti Eterociclici e loro Applicazioni - C.N.R., Università di Firenze, via G. Capponi 9, I-50121 Firenze, Italy. cordero@chimorg.unifi.it
Gensini
M
M
Goti
A
A
Brandi
A
A
D006900:Hydroxylation; D007202:Indicators and Reagents; D007212:Indolizines / Q000138:chemical synthesis* / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009589:Nitrogen Oxides; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D007202:Indicators and Reagents; D007212:Indolizines; D009589:Nitrogen Oxides; C015388:nitrones