Step G: 4-(4-methoxyphenyl)-4-oxobutanoic acid (40 g) was suspended in a solvent mixture of acetic acid (100 ml) and tetrahydrofuran (THF, 100 ml). To this suspension, 10% palladium-carbon catalyst (50% wet weight, 4 g) was added, followed by stirring the reaction mixture under hydrogen atmosphere (0.4 MPa) for 9 hours. Upon completion of the reaction, it was filtered through a diatomaceous earth pad to remove the catalyst. Toluene was added to the filtrate and the solvent was subsequently removed by distillation under reduced pressure to afford 4-(4-methoxyphenyl)butanoic acid in quantitative yield. The product was characterized by 1H-NMR (CDCl3): δ 1.89 (m, 2H), 2.32 (t, J=7.3 Hz, 2H), 2.58 (t, J=7.4 Hz, 2H), 3.73 (s, 3H), 6.78-6.82 (m, 2H), 7.03-7.08 (m, 2H), 10.96 (brs, 1H).
