Diisopropylethylamine → {(2S,3S)-3-hydroxy-2-[2-(4-trifluoromethyl-1H-benzoimidazol-2-yl)-acetylamino]-hex-4-ynyl}-carbamic acid benzyl ester (HRID 2377552)｜HGS AIchem

実験手順

N-(2-Nitro-3-trifluoromethyl-phenyl)-acetamide (Helvetica 1947, p. 107) (3.6 g) was dissolved in EtOH and heated to 105° C. prior to the addition of 1N NaOH (60 ml) and 50% NaOH (10 ml). After 2.5 h, the reaction was cooled to rt and EtOAc was added. The organic layer was washed with water and brine. Then it was dried and concentrated to give a crude 2-nitro-3-trifluoromethyl-phenylamine (2.79 g): 1H NMR (CDCl, δ ppm, 300 mHz) 5.0 (s, 2H), 7.02 (d, 1H), 7.10 (d, 1H), 7.38 (t, 1H). A portion (1.42 g) of this material was dissolved in MeOH (20 mL) prior to the addition of 10% Pd/C (260 mg). The reaction was placed on a Parr apparatus under hydrogen at 60 psi for 3 h. The Pd/C was filtered off and solvent was concentrated to give 3-trifluoromethyl-benzene-1,2-diamine (1.16 g): 1H NMR (CDCl, δ ppm, 300 mHz) 3.40 (s, 2H), 3.94 (s, 2H), 6.70 (t, 1H), 6.85 (d, 1H), 7.02 (d, 1H). A portion (1.15 g) of this material was dissolved in diethyl malonate. The reaction was heated at 160° C. (oil bath temperature) for 1.5 h. After cooling to rt, flash chromatography of the crude reaction gave (4-trifluoromethyl-1H-benzoimidazol-2-yl)-acetic acid ethyl ester (1.14 g). MS found: (M+H)+=273.0. A portion (200 mg) of this material was dissolved in THF (2 mL) prior to the addition of a solution of LiOH.H2O (37 mg) in water (0.1 ml). A couple drops of MeOH were added until the solution became clear. After 2 h at rt, the reaction was concentrated and freeze-dried to provide (4-trifluoromethyl-1H-benzoimidazol-2-yl)-acetic acid lithium salt (175 mg). MS found: (M+H)=245.0 (28b) The compound [(2S,3S)-2-amino-3-hydroxy-hex-4-ynyl]-carbamic acid benzyl ester (70 mg, 0.19 mmol, prepared as described in WO PCT 0250019) was dissolved in 5 mL of 2:1 CH2Cl2/DMF. The resultant solution was charged sequentially with the lithium salt of (4-trifluoromethyl-1H-benzoimidazol-2-yl)-acetic acid (46 mg, 0.19 mmol, see procedure 28a), N,N-diisopropylethylamine (0.16 mL, 0.94 mmol) and HATU (85 mg, 0.22 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-(4-trifluoromethyl-1H-benzoimidazol-2-yl)-acetylamino]-hex-4-ynyl}-carbamic acid benzyl ester (87 mg, 95% yield). MS found: (M+Na)+=511.3. (28c) A solution of {(2S,3S)-3-hydroxy-2-[2-(4-trifluoromethyl-1H-benzoimidazol-2-yl)-acetylamino]-hex-4-ynyl}-carbamic acid benzyl ester (87 mg, 0.18 mmol) in MeOH (3 mL) was charged with 5% Pd/C, Degussa style (17 mg), stirred under H2 (1 atm) for 12 h at RT, filtered, and concentrated in vacuo. The residue was dissolved in MeOH (3 mL). The resultant solution was charged sequentially with 2,4-dimethylbenzaldehyde (0.024 mL, 0.16 mmol) and sodium cyanoborohydride (12 mg, 0.2 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)+=477.4.