Sulfuric Acid → (S)-2-methyl-5-phenylpentanoic acid

Participants

Reaction Conditions

Reaction Steps

To a solution consisting of (S)—N—((R)-2-hydroxy-1-phenylethyl)-2-methyl-5-phenylpentanamide (19mb(i), 3.5 g, 11.24 mmol) in 1,4-dioxane (80 mL) was added aqueous sulfuric acid (36 mL, 3 N solution) and the mixture was stirred overnight at 80° C. The reaction mixture was extracted with ethyl acetate three times and the organic layers were combined, dried over sodium sulfate, filtered, and concentrated under vacuum. The residue was purified by silica gel chromatography. Elution with ethyl acetate-heptane-acetic acid (30:70:0.4 v/v/v) afforded the title compound (2.4 g, quantitative yield) as a clear oil; Rf 0.48 (solvent system: 30:70:0.4 v/v/v ethyl acetate-heptane-acetic acid; HPLC retention time 26.0 minutes; Chiralpak IA, 5μ, 4.6×25 mm, ultraviolet detector at 208 nm 0.75 ml/min 99:1:0.5 v/v heptanes-2-propanol-acetic acid; MS (ESI−) m/z 191.1 (M−H)−; 1H-NMR (CDCl3) δ 7.33-7.27 (m, 2H), 7.22-7.16 (m, 3H), 2.67-2.60 (m, 2H), 2.56-2.46 (m, 1H), 1.80-1.60 (m, 3H), 1.59-1.36 (m, 1H), 1.25-1.14 (m, 3H); [α]Tλ=α/cl, [α]21.9D=+0.089/(0.01501 g/1.5 mL)(0.5)=+17.79° (c=1, CHCl3).

Provenance & Evidence