ethyl cis-6-aza-7-butyl-5-oxa-2-{[(3-chlorophenyl)amino]carbonylamino}spiro[3.4]oct-6-ene-2-carboxylate

ethyl cis-2-amino-6-aza-5-oxa-7-phenylspiro[3.4]oct-6-ene-2-carboxylate

ethyl cis-2-amino-6-aza-7-(4-bromophenyl)-5-oxaspiro[3.4]oct-6-ene-2-carboxylate