α,β-Unsaturated Carboxylic Acid Derivatives. XIII. The Synthesis and Configuration of Alkyl 2-Acylamino-2-alkenoates and Their Cyclized 2,5-Piperazinedione Derivatives

It is described that alkyl (E)- and (Z)-2-halo (Cl, Br, and I)-acetylamino-2-alkenoate (DHA), obtained by the condensation of alkyl 2-oxoalkanoate with chloro- or bromoacetamide and by halogen exchange from the chlorine of DHA to iodine, are cyclized with ammonia or hydroxylamine to give the (E)- and (Z)-isomers of unsymmetric 3-alkylidene-2,5-piperazinediones and their 1-hydroxy derivatives respectively. Alkyl (E)- and (Z)-2-iodoacetylamino-2-alkenoates were converted into the corresponding acetylamino- and phthalimidoacetylamino derivatives. The configurations of all the DHA and 2,5-piperazinedione derivatives were determined from the NMR spectra data.