Trifluoroacetic acid → 3-Methyl-3(2,4,6-trimethoxyphenylmethylthio)butyric acid

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To a solution of 3-mercapto-3-methylbutyric acid (Sweetman et al, J. Med. Chem., 14:868 (1971)) (4.6 g, 34 mmol) in methylene chloride (250 ml) under nitrogen and cooled over ice/salt to 5° C. (internal temperature) was added trifluoroacetic acid (82 g, 0.72 mol). No significant temperature rise was noted during the addition. To this was then added dropwise a solution of 2,4,6-trimethoxybenzyl alcohol (Munson et al, J. Org. Chem., 57:3013 (1992)) (6.45 g. 32 mmol) in methylene chloride (150 ml) such that the reaction temperature does not rise above 5° C. After the addition was complete, the mixture was stirred for an additional 5 minutes at 5° C. and the volatiles were removed in vacuo (toluene or ethyl acetate can be used to assist in the removal of volatile material). The residue was partitioned between diethyl ether and water and the organic phase dried over anhydrous sodium sulfate, filtered and the volatile material removed in vacuo. The residue was treated with activated charcoal and recrystalized from diethyl ether/hexane. The product was isolated as a white solid in 70% yield (7 g); mp 103-105° C. 1H NMR (CDCl3) δ 6.12 (s, 2 H), 3.80-3.85 (m, 11 H), 2.74 (s, 2 H), 1.47 (s, 6 H). 13C NMR (CDCl3) δ 173.9, 160.6, 158.6, 105.6, 90.5, 55.7, 55.3, 45.9, 43.6, 28.4, 21.0.

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