Benzyl 4-[5-chloro-1-(2-ethoxy-2-oxoethyl)-6-oxo-1,6-dihydropyridazin-4-yl]piperazine-1-carboxylate4-[5-Chloro-1-(2-ethoxy-2-oxoethyl)-6-oxo-1,6-dihydropyridazin-4-yl]piperazine, N1-CBZ protectedBenzyl 4-[5-chloro-1-(2-ethoxy-2-oxoethyl)-6-oxo-1 ,6-dihydro-4-pyridazinyl]tetrahydro-1(2H)-pyrazinebenzyl 4-[5-chloro-1-(2-ethoxy-2-oxoethyl)-6-oxo-1,6-dihydro-4-pyridazinyl]tetrahydro-1(2H)-pyrazinecarboxylate