(3aR,6aR)-Tetrahydro-4-(phenylmethyl)-2H-furo[3,2-b]pyrrole-2,5(3H)-dione is an intermediate in synthesizing Monocrotaline-d4 (M526002), a labelled Monocrotaline (M526000) which is a toxic pyrrolizidine alkaloid isolated from Crotalaria spp. It is used for inducing pulmonary diseases in rats.