Expeditious synthesis of bicyclic pyrrolidine/pyrrolizidine/thiazolidine grafted macrocycles through intramolecular 1,3-dipolar cycloaddition of azomethine ylides

Stereoselective synthesis of bicyclic pyrrolidine and pyrrolizidine grafted macrocycles has been accomplished through intramolecular 1,3-dipolar cycloaddition (1,3-DC) reaction. Alkenyl aldehydes 4a–b derived from salicylaldehyde have been reacted with secondary aminoacids to generate azomethine ylides which in turn were trapped intramolecularly by suitably placed dipolarophiles to give the corresponding macrocycle in moderate yield. The structures were assigned by 2D NMR spectra and the regio- and stereochemical outcome of the cycloadducts was established by a single crystal X-ray analysis of one of the products.