(S)-tert-Butyl 4-(4-((benzyloxy)carbonyl)-3-(cyanomethyl)piperazin-1-yl)-2-(methylthio)-5,6-dihydropyrido[3,4-d]pyrimidine-7(8H)-carboxylate

(S)-tert-Butyl 4-(4-((benzyloxy)carbonyl)-3-(cyanomethyl)piperazin-1-yl)-2-(methylthio)-5,6-dihydropyrido[3,4-d]pyrimidine-7(8H)-carboxylate