Methanol → 4-(S)-Acetylthio-5-t-butyldiphenylsilyloxypentanoic acid, methyl ester

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Reaction Steps

Thioacetic acid (1 mL, 13.2 mmol) was added to 20 mL of toluene under a nitrogen atmosphere. A 1 M solution of tetrabutylammonium hydroxide in methanol (11 mL, 11 mmol) with a washing of 1 mL methanol was added to the thioacetic acid solution. The methanol was removed azeotropically with toluene and residual salt redissolved in 30 mL toluene. The salt solution with a washing of 20 mL toluene was added to a solution of 8 (4.75 g, 9.6 mmol) in 50 mL toluene and stirred under nitrogen for 18 hours. After removal of solvent and precipitated salts, the crude product was purified by flash chromatography with 6:1 hexane/ethyl acetate. Yield 3.47 g (81%) of a viscous oil [α]D25 -16.0° (C=0.7, CDCl3); FAB MS 445 (M+H)+, 387 (M-t-butyl)+ ; 1H NMR (CDCl3) δ 7.65 (m, 4, ArH), 7.4 (m, 6, ArH), 3.8 (m, 1, H-4), 3.7 (s, 3, OCH3), 3.7 (m, 2, CH2), 2.35 (m, 2, CH2), 2.3 (s, 3, acetyl CH3), 2.2 (m, 1, H-2), 1.9 (m, 1, H-2), 1.05 (s, 9, t-butyl).

Provenance & Evidence