To a solution of (S)-tert-butyl 2-amino-3-cyclohexylpropyl(methyl)carbamate (326 mg, 1 mmol), DIEA (258 mg, 2 mmol) and methyl 2-((R)-(3-chlorophenyl)((R)-piperidin-3-yl)methoxy)ethylcarbamate (270 mg, 1 mmol) in ethyl acetate (6 mL) was added dropwise a solution of di-imidazol-1-yl-methanethione (194 mg, 1 mmol) in ethyl acetate (4 mL) at 0-5° C. After addition, the mixture was allowed to warm to room temperature for 3-4 h, the mixture was washed with water (20 mL) and brine (20 ml), the organic layer was dried over Na2SO4, filtered and concentrated in vacuo to give the residue, which was purified by preparative TLC to afford methyl 2-((R)-(3-chlorophenyl)((R)-1-((S)-1-cyclohexyl-3-(N-methyl-N-(tert-butoxycarbonyl)amino)propan-2-ylcarbamothioyl)piperidin-3-yl)methoxy)ethylcarbamate. MS ESI +ve m/z 638 (M+H).
