4-Nitrobenzoic Acid → (3R,5S)-1-((1R,2S)-1-(ethoxycarbonyl)-2-vinyl-cyclopropylcarbamoyl)-5-(hex-5-enyl(methyl)carbamoyl)pyrrolidin-3-yl 4-nitrobenzoate

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Reaction Steps

To a solution of 4-nitrobenzoic acid (3.1 g, 1.5 eq) in CH2Cl2 (61 mL) were added dropwise 3.1 mL oxalyl chloride (3 eq), followed by 60 μL DMF. The reaction mixture was stirred at room temperature for 2 hrs and concentrated in vacuo. A solution of the resulting solid in CH2Cl2 (30 mL) was added dropwise to a solution of compound 50 (5.0 g, 1 eq) and triethylamine (3.4 mL, 2 eq) in CH2Cl2 (30 mL). The reaction mixture was stirred at room temperature for 2 hrs, and then washed with water and a saturated aqueous solution of sodium carbonate. The aqueous layer was extracted with CH2Cl2. The combined organic phases were dried on sodium sulphate, filtered, and concentrated to dryness. Recrystallisation with TBME gave compound BI as a yellow powder, and the filtrate was submitted to flash chromatography using CH2Cl2/MeOH as an eluant, affording a total of 6.42 g of compound BI in 93% yield.

Provenance & Evidence