(-)-(R)-N-((R)-2-hydroxy-1-phenylethyl)-2-methyl-5-phenylpentanamide → (2R)-5-Phenyl-2-methylpentanoic acid

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Reaction Steps

-(−)-2-Methyl-5-phenylpentanoic acid was prepared from 19mc(i) (30 g) in the same manner (S)-(+)-2-methyl-5-phenylpentanoic acid was prepared from 19mb(i) as described above. The residue was purified by silica gel chromatography. Elution with ethyl acetate-heptane-acetic acid (20:80:0.4 v/v/v) afforded the title compound (20.8 g) as a clear oil; TLC Rf 0.51 (solvent system: 30:70:1 v/v/v ethyl aceate-hepatane-acetic acid; HPLC retention time 24.46 min; Chiralpak IA 4.6×25 mm 5μ, at a wavelength of 208 nm 0.75 mL/min, 99:1:0.5 heptane: 2-propanol:acetic acid, chiral purity 99.32% (R), 0.68% (S); MS (ESI−) m/z 191.1 (M−H)−; 1H-NMR (CDCl3) δ 7.31-7.26 (m, 2H), 7.21-7.15 (m, 3H), 2.67-2.57 (m, 2H), 2.54-2.44 (m, 1H), 1.79-1.59 (m, 3H) 1.58-1.41 (m, 1H), 1.18 (d, J=6.96 Hz, 3H).

Provenance & Evidence