(S)-tert-Butyl 2-((tert-butoxycarbonyl)amino)-5-((1-trityl-1H-imidazo[4,5-b]pyridin-2-yl)amino)pentanoate-d3 is an intermediate in the synthesis of Pentosidine-d3 TFA Salt which is a biochemical marker of bone turnover for management of metabolic bone diseases.