Triphosgene → (2R,4S)-5-biphenyl-4-yl-4-isocyanato-2-methyl-pentanoic acid ethyl ester

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Reaction Steps

To a vigorously stirred 1:1 mixture of methylene chloride/8% aqueous NaHCO3 (30 mL) at 0° C. is added triphosgene (114 mg, 0.384 mmol). After stirring the mixture at 0° C. for 5 minutes, (2R,4S)-4-amino-5-biphenyl-4-yl-2-methyl-pentanoic acid ethyl ester hydrochloride (Intermediate 29: 400 mg, 1.15 mmol) is added and stirring is continued for 15 minutes. The organic phase is separated and dried over sodium sulfate. The solvent is removed under reduced pressure to furnish (2R,4S)-5-biphenyl-4-yl-4-isocyanato-2-methyl-pentanoic acid ethyl ester.

Provenance & Evidence