methyl (3R,7aR)-3-(tert-butyl)-5,7-dioxo-6-phenyldihydro-1H,3H-pyrrolo[1,2-c]oxazole-7a(5H)-carboxylate

methyl (3R,7aR)-7-(benzyloxy)-3-(tert-butyl)-6-methyl-5-oxo-1H,3H-pyrrolo[1,2-c]oxazole-7a(5H)-carboxylate