2-Aryl-4-(ethoxycarbonyl)oxazolidines and thiazolidines (1) were prepared from the corresponding α-amino acid ethyl esters containing either hydroxyl or mercapto groups in the β-position by fusion with some aromatic aldehydes. Dehydrogenation of 1 with N-bromosuccinimide gave the corresponding oxazoles and thiazoles. The oxazolidines and thiazolidines gave Mannich bases on interaction with p-nitrobenzaldehyde and piperidine. Acetylation of 1 gave the corresponding N-acetylderivatives, which on fusion in the presence of anhydrous ZnCl2 undergo cyclization, giving the corresponding bicyclic compounds, 5,6,7,8-tetrahydro-1H,3H-pyrrolo[1,2-c]oxazole (or thiazole)-1,3-diones.