Diethylamine → [(1-{(S)-2-[(R)-2-(9H-Fluoren-9-ylmethoxycarbonylamino)-3-phenyl-propionylamino]-3-tritylsulfanyl-propionylamino}-cyclopropanecarbonyl)-amino]-acetic acid methyl ester

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Reaction Steps

To a solution of 1 (300 mg, 0.40 mmol, 1 eq) in MeCN (8 mL) was added Et2NH (0.8 mL, 10% v/v) dropwise at rt under Ar(g). The solution was stirred at rt for 2 h, then the solvent was removed in vacuo. The excess of amine was co-evaporated with MeCN (3×5 mL), then with a 1:5 mixture of CH2Cl2/hexane (10 mL). A white solid was obtained and the flask was dried under high vacuum for 2 h. To a solution of Fmoc-D-Phenylalanine (173 mg, 0.45 mmol, 1.1 eq) in MeCN (7 mL) at 0° C. was added PyBOP (233 mg, 0.45 mmol, 1.1 eq) and 176 μL of N-ethyldiisopropylamine (1.01 mmol, 2.5 eq) under Ar(g). The crude amine, dissolved in CH2Cl2 (6 mL) was added to the mixture dropwise. The reaction mixture was then left to warm to rt overnight. The mixture was then concentrated in vacuo and the residue was further purified by silica gel column chromatography with hexane/EtOAc (1:2→0:1) to yield 2 as a white solid (294 mg, 82%).

Provenance & Evidence