Treatment of syn-oximes of 5-substituted 2-(3-chloropropanoylamino)benzophenones with equimolar amount of sodium hydroxide results in formation of syn-oximes of 5-substituted 2-propenoylaminobenzophenones. The corresponding anti isomers under the same conditions give a mixture of anti-oximes of 5-substituted 2-(propenoylamino)benzophenones and 18-membered 11,22-disubstituted 7,8,18,19-tetrahydrodibenzo[d,m][1,10,2,6,11,15]dioxatetraazacyclooctadecine-6,17(5H,16H)-diones.