A mixture of (R)-2-(benzyloxycarbonylamino)-3-methyl-3-(2-nitrophenylthio)butanoic acid (18.3 g, 45.2 mmol, Eq: 1.00), NH4Cl (4.84 g, 90.5 mmol, Eq: 2) and Zn (45.9 g, 701 mmol, Eq: 15.5) in MeOH (500 mL) was heated at reflux for 6 h and the mixture was filtered through Celite. The filter cake was washed with hot MeOH. The filtrate was concentrated, the residue was tritrurated with H2O, 1:3 Et2O/Hexane and azeotroped with toluene. The resulting material was dried under vacuum to give (R)-3-(2-aminophenylthio)-2-(benzyloxycarbonylamino)-3-methylbutanoic acid (16.9 g, 100%) which was used without purification.
