1-Ethyl-3-(3'-dimethylaminopropyl)carbodiimide → (19S,23 S)-tri-tert-butyl 1-(1-(2-(bis(2-tert-butoxy-2-oxoethyl)amino)-2-oxoethyl)-1H-imidazol-2-yl)-2-((1-(2-(bis(2-tert-butoxy-2-oxoethyl)amino)-2-oxoethyl)-1H-imidazol-2-yl)methyl)-13,21-dioxo-2,14,20,22-tetraazapentacosane-19,23,25-tricarboxylate

Participants

Reaction Steps

A solution of (S)-di-tert-butyl 2-(3-((S)-6-amino-1-tert-butoxy-1-oxohexan-2-yl)ureido)pentanedioate (85 mg, 0.174 mmol), 11-(bis((1-(2-(bis(2-tert-butoxy-2-oxoethyl)amino)-2-oxoethyl)-1H-imidazol-2-yl)methyl)amino)undecanoic acid (118 mg, 0.127 mmol), EDCI (38 mg, 0.20 mmol), HOBt (26 mg, 0.20) and DIPEA (0.30 mL) in DCM (5.0 mL) was stirred at rt for overnight. The reaction mixture was purified by biotage eluting with 1% to 10% MeOH in DCM to afford (19S,23S)-tri-tert -butyl 1-(1-(2-(bis(2-tert-butoxy-2-oxoethyl)amino)-2-oxoethyl)-1H-imidazol-2-yl)-2-((1-(2-(bis(2-tert-butoxy-2-oxoethyl)amino)-2-oxoethyl)-1H-imidazol-2-yl)methyl)-13,21-dioxo-2,14,20,22-tetraazapentacosane-19,23,25-tricarboxylate (38 mg, 21%) as a colorless oil. 1H NMR (400 MHz, CDCl3) 6.95 (d, J=1.2 Hz, 2 H), 6.83 (d, J=0.80 Hz, 2 H), 5.97 (s, 1 H), 5.28 (d, J=7.6 Hz, 1 H), 5.23 (d, J=8.4 Hz, 1 H), 4.94 (s, 4 H), 4.33-4.25 (m, 2H), 4.12 (s, 4 H), 4.03 (s, 4 H), 3.63 (s, 4 H), 3.25-3.16 (m, 2 H), 2.53 (t, J=7.4 Hz, 2 H), 2.33-2.24 (m, 2 H), 2.15 (t, J=7.6 Hz, 2 H), 2.08-2.03 (m, 2 H), 2.02-1.20 (m, 85 H); MS (ESI), 701.6 (M/2+H)+.

Provenance & Evidence