(S)-2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)-5-((5,9-dioxo-4,10-dioxa-6,8-diazatrideca-1,12-dien-7-ylidene)amino)pentanoic acid

(S)-2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)-5-((5,9-dioxo-4,10-dioxa-6,8-diazatrideca-1,12-dien-7-ylidene)amino)pentanoic acid,