Succinate → tert-Butyl ((2S,4S,5S)-5-(2-(2,6-dimethylphenoxy)acetamido)-4-hydroxy-1,6-diphenylhexan-2-yl)carbamate

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Reaction Steps

Oxallyl chloride (36.3 ml, 0.42 mol) was added to a slurry of 2-6 dimethylphenoxyacetic acid (50 g, 0.28 mol) in 500 ml toluene followed by addition of 5 drops of DMF and stirred at room temperature for 30 min, then at 55° C. for 1.5 hours. The toluene was removed on a rotary evaporator and remaining volatiles were removed in vacuo to afford 2,6-dimethylphenoxyacetyl chloride as an amber oil, 55 grams, 100%. [2S,3S,5S]-2-Amino-3-hydroxy-5-t-butyloxycarbonylamino-1,6-diphenylhexane×0.5 succinate (111.9 g, 0.25 mol) was charged to a 2 L, 3-necked round-bottomed flask with mechanical stirring. NaHCO3 (106 9, 1.26 mol), 600 ml H2O and 600 ml EtOAc were added and stirred vigorously until all solids were dissolved (15 minutes). Stirring was slowed and a solution of the 2,6-dimethyl-phenoxyacetyl chloride and EtOAc (100 ml) was added in a narrow stream via addition funnel. After 30 min of stirring, starting materials were consumed (HPLC analysis) and the layers were separated. The aqueous layer was extracted with EtOAc, the organic layers were combined and washed with 200 ml of 1 M NaOH, 200 ml of 10% HCl, 200 ml of brine, dried over MgSO4, filtered and concentrated to provide the desired product as a white solid.

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