To a stirring solution of #114 (164 mg, 0.259 mmol, 1.0 eq.) and 1-(tert-butoxycarbonyl)-2-methyl-D-proline (71.3 mg, 0.311 mmol, 1.2 eq.) in 4 mL of dichloromethane, HATU (118 mg, 0.311 mmol, 1.2 eq.) was added followed by Hunig's base (0.180 mL, 1.04 mmol, 4 eq.). The reaction was allowed to stir at room temperature for -30 minutes. Reaction was reduced down. Reaction was taken up in 3.5 mL of dichloromethane and placed under nitrogen. To this stirring solution, TFA (1.5 mL, 20 mmol, 76 eq.) was added. The reaction was allowed to stir at room temperature for -1 hour. Reaction was reduced down and placed underneath high vacuum. Purification by (Method J*) affords #131 (119 mg, 54%) as a white solid. HPLC (Protocol A at 45° C.): m/z 744.5 [M+H+], retention time=7.342 minutes (purity >98%). 1H NMR (400 MHz, DMSO-d6), δ 9.08-9.18 (m), 8.79-8.89 (m), 8.76 (t), 8.54 (d), 8.29 (d), 7.14-7.31 (m), 4.70-4.79 (m), 4.57-4.66 (m), 4.45-4.55 (m), 3.96-4.04 (m), 3.74-3.80, 3.66 (d), 3.48-3.61 (m), 3.40-3.48 (m), 3.09-3.34 (m), 3.00-3.09 (m), 2.95-3.00 (m), 2.83-2.93 (m), 2.36-2.53 (m), 2.21-2.35 (m), 2.10-2.19 (m), 1.99-2.10 (m), 1.61-1.09 (m), 1.36-1.53 (m), 1.21-1.35 (m), 1.02-1.10 (m), 0.94-1.0 (m), 0.86-0.93 (m), 0.73-0.82 (m).
