The compound [(2S,3S)-2-amino-3-hydroxy-hex-4-ynyl]-carbamic acid benzyl ester (173 mg, 0.46 mmol, prepared as described in WO PCT 0250019) was dissolved in 5 mL of 1:1 CH2Cl2/DMF. The resultant solution was charged sequentially with 2-methyl-malonic acid (54 mg, 0.46 mmol), meta-trifluoromethylaniline (0.06 mL, 0.46 mmol), N,N-diisopropylethylamine (0.8 mL, 4.6 mmol) and HATU (434 mg, 1.1 mmol). The mixture was stirred for 12 h at RT, concentrated in vacuo, and partitioned between EtOAc and sat. NH4Cl. The aqueous phase was extracted with EtOAc (1×). The combined organic extracts were washed with sat. NaHCO3 and brine, dried (Na2SO4), filtered, and concentrated in vacuo. The residue was purified by flash chromatography to provide {(2S,3S)-3-hydroxy-2-[2-(3-trifluoromethyl-phenylcarbamoyl)-propionylamino]-hex-4-ynyl}-carbamic acid benzyl ester (40 mg, 17% yield). MS found: (M+Na)+=528.4. (25b) A solution of {(2S,3S)-3-hydroxy-2-[2-(3-trifluoromethyl-phenylcarbamoyl)-propionylamino]-hex-4-ynyl}-carbamic acid benzyl ester (40 mg, 0.08 mmol) in MeOH (2 mL) was charged with 5% Pd/C, Degussa style (8 mg), stirred under H2 (1 atm) for 12 h at RT, filtered, and concentrated in vacuo. The residue was dissolved in MeOH (2 mL). The resultant solution was charged sequentially with 2,4-dimethylbenzaldehyde (0.009 mL, 0.06 mmol) and sodium cyanoborohydride (5 mg, 0.08 mmol), stirred for 12 h at RT, quenched with sat. NaHCO3, and extracted twice with EtOAc. The organic extracts were combined, washed with brine, dried (Na2SO4), filtered, and concentrated in vacuo. Purification of the residue by reverse-phase HPLC provided the title compound as a white powder after lyopholization. MS found: (M+H)+=494.4.
