Acetonitrile → (R)-4-((E)-(S)-3-Hydroxy-7-tritylsulfanyl-hept-4-enoylamino)-4-{(S)-1-[1-(methoxycarbonylmethyl-carbamoyl)-1-methyl-ethylcarbamoyl]-2-tritylsulfanyl-ethylcarbamoyl}-butyric acid tert-butyl ester

Participants

Reaction Steps

To a solution of 5 (1.60 g, 1.73 mmol, 1 eq) in MeCN (35 mL) was added at rt diethylamine (3.5 mL, 10% v/v) dropwise. One hour later, the solution was concentrated in vacuo and co-evaporated with MeCN (2×10 mL), then with CH2Cl2/hexane (5 mL). The resultant oil was then dried under high vacuum for 3 h. To a solution of (E)-(S)-3-hydroxy-7-tritylsulfanyl-hept-4-enoic acid (758 mg, 1.81 mmol, 1.05 eq) and PyBOP (988 mg, 1.90 mmol, 1.1 eq) in MeCN (25 mL) was added at 0° C. diisopropylethylamine (0.75 mL, 4.3 mmol, 2.5 eq) dropwise. After 5 min, the crude amine solution in CH2Cl2 (25 mL) was added dropwise to the reaction mixture. The solution was then warmed to rt overnight. The solvent was removed in vacuo. Purification by column chromatography on silica (eluting with hexane/EtOAc, 1:4) yielded 6 (1.61 g, 1.46 mmol, 85%) as a white solid.

Provenance & Evidence