Diisopropylethylamine → (2S)-tert-butyl 2-(4-(methoxy)-1-(4-bromophenyl)-1,4-dioxobutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

HATU (10.5 g, 27.6 mmol) was added to a solution of Example J6, methyl 3-amino-4-(4-bromophenyl)-4-oxobutanoate (10 g, 27.6 mmol), (S)—N-Boc-proline (7.13 g, 33.1 mmol), and Hunig's Base (45 mL, 276 mmol) in DMF (150 mL) and stirred for 18 hours at 24° C. The reaction was diluted with ethyl acetate (2 vol) and H2O (¼ vol) and sat NaHCO3 (⅛ vol). Filter through diatomaceous earth (Celite®) to remove tin salts. Extract aqueous layer (2×) with ethyl acetate, and concentrate combined organic to remove solvents (high vacuum on rotory evaporator). The residue was subject to a short silica gel chromatography to remove by-products, and the resultant crude product was charged (CH2Cl2) a 65 (M) Biotage silica gel cartridge. Gradient elution 15-70% B over 2 L (A=Hexanes; B=ethyl acetate) gave a less polar band of (2S)-tert-butyl 2-(4-(benzyloxy)-1-(4-bromophenyl)-1,4-dioxobutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate 1.35 g (8.7%) and more polar Example J7, (2S)-tert-butyl 2-(4-(methoxy)-1-(4-bromophenyl)-1,4-dioxobutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate 7.6 g (49%). RT=2.0 minutes (condition 1); LCMS: Anal. C21H27BrN2O6 Calcd. 383; found: 383 (M-Boc).

Provenance & Evidence