Trifluoroacetic acid → 4-Benzyl-1-[2(R)-tert-butoxycarbonylamino-3-triphenylmethylthiopropyl]-2(S)-(2-methoxyethyl)piperazine

関与物質

反応条件

反応手順

4-Benzyl-1-tert-butoxycarbonyl-2(S)-(2-methoxyethyl)piperazine from Example 7, step C (1.17 g, 3.50 mmol) was dissolved in methylene chloride (20 mL). To this solution was added trifluoroacetic acid (10 mL) and the reaction stirred at 20° C. for 1 h. The volatiles were removed in vacuo and the residue taken up in dichloroethane (40 mL). Triethylamine was added to attain pH 7. To this solution was added crushed molecular seives (1 g), sodium triacetoxyborohydride (1.2 g, 5.3 mmol) and the reaction cooled to -15° C. with ice-methanol. A solution of 2(R)-tert-butoxycarbonylamino-3-triphenylmethylthiopropanal (1.72 g, 3.85 mmol) in dichloroethane (15 mL) was added slowly dropwise. The reaction was stirred at 20° C. overnight then quenched with saturated sodium bicarbonate. The organic phase was washed with saturated sodium chloride solution, and dried over magnesium sulfate. The crude product (2.52 g) was chromatographed on silica gel with 30% ethyl acetate in hexane using medium pressure liquid chromatography (MPLC). The title compound (Rf 0.21) was isolated as a gum (0.906 g). NMR (CHCl3, 300 MHz) δ 7.2-7.4 (20H, m), 4.70 (1H, d, J=8 Hz), 3.63 (1H, br s), 3.50 (1H, d, J=13 Hz), 3.36 (1H, d, J=13 Hz), 3.2-3.35 (5H, m), 2.75 (1H, m), 2.0-2.6 (10H, m), 1.75 (2H, m), 1.42 (9H, s). A diastereomeric minor product (Rf 0.14) was also isolated (0.065 g).

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