Microwave-assisted synthesis and odor characteristics of some new isoxazolidines

We describe herein the design and synthesis of new isoxazolidin-5-carboxylates by microwave-assisted 1,3-dipolar cycloadditions of aldonitrones, derived from five fragrant aldehydes, with methacrylate esters. The reaction proceeded regioselectively providing mostly endo- diastereomers and in some cases an inseparable mixture of endo-exo products. The structures of target compounds were identified on the basis of IR, NMR, and TOF-MS measurements. Besides, both aldonitrone and isoxazolidine derivatives were subjected to olfactory evaluation by an expert nose. Diverse fragrance notes were observed in each series of isoxazolidines bearing different groups from aldonitrones. However, their odor ranges were found as animalic, medical, waxy, and ozonic undertones in common.