Oxalyl chloride → (+)-(2R,3S)-3-(3,4-dimethoxyphenylsulfanyl)-2-methyl-7-phenylheptanoic acid hydroxyamide

Participants

Reaction Conditions

Reaction Steps

(2R,3S)-3-(3,4-Dimethoxyphenylsulfanyl)-2-methyl-7-phenylheptanoic acid (0.46 g, 1.2 mmol) is dissolved in CH2Cl2 (4.5 mL) and cooled to 0° C. and to this is added 2 M oxalyl chloride in CH2Cl2 (1.9 mL, 3.8 mmol) over 5 minutes. The ice bath is removed and the reaction allowed to warm to room temperature. After 1.5 hours, the reaction is concentrated in vacuo and azeotroped with chloroform several times. The crude residue is dissolved in CH2Cl2 (4 mL) and O-trimethylsilylhydroxylamine (0.4 g, 3.6 mmol) is added slowly. After 5 minutes, the reaction is diluted with CH2Cl2 (20 mL) and washed with 2 N HCl (15 mL). The aqueous layer is back-extracted with CH2Cl2 (10 mL) and the combined organic layers are washed with water (50 mL), dried over MgSO4 and concentrated in vacuo. The crude residue is azeotroped with ether/petroleum ether and triturated with a large volume of petroleum ether to give (+)-(2R,3S)-3-(3,4-dimethoxyphenylsulfanyl)-2-methyl-7-phenylheptanoic acid hydroxyamide (0.45 g, 94%): [a]D23 +22° (c=1.0, CHCl3); 1H NMR (300 MHz, CD3OD) δ 7.25-7.21 (m, 2H), 7.15-7.10 (m, 3H), 7.05-6.98 (m, 2H), 6.87 (d, J=8.2 Hz, 1H), 3.81 (s, 3H), 3.80 (s, 3H), 3.17-3.14 (m,1H), 2.58-2.52 (m, 2H), 2.35-2.30 (m, 1H), 1.75-1.65 (m, 1H), 1.60-1.40 (m, 5H), 1.17 (d, J=7.0 Hz, 3H); MS (ion spray) m/e 404 (M+H)+ ; Anal. (C22H29NO4S) C, H, N.

Provenance & Evidence