PMGB

A mixture of the ester (0.022 mol) and sodium borohydride (0.039 mol) in 250 mL anhydrous ethanol was refluxed for overnight (12 h). The reaction mixture was concentrated, the semi solid residue was diluted with 250 mL of dichloromethane, washed with 250 mL of saturated aqueous NaHCO₃ solution, dried (Na₂SO₄) and evaporated under reduced pressure to give the corresponding alcohol which was purified by silica gel column chromatography (using a gradient of hexane and ethyl acetate) followed by triturating with ether (white solid, 22% yield).

¹H NMR (400 MHz, CDCl₃): d 2.40 (t, J = 7.6 Hz, 2H); 2.81 (t, J = 7.2 Hz, 2H); 4.38 (d, J = 5.6 Hz, 2H); 5.11 (t, J = 5.6 Hz, 1H); 6.80-6.82 (m, 2H); 7.06 (d, J = 8.0 Hz, 1H); 10.04 (s, 1H).

To a solution of the ester (0.004 mol) in 8 mL ethanol was added 4 mL 1N aq. NaOH solution. The resulting mixture was stirred at rt for overnight (12 h). The reaction mixture was concentrated and the residue (water solution) was cooled in an ice bath and acidified with 10 mL of 1N HCl solution until pH 6. The white precipitate (product) formed was filtered and washed with water and air dried to give the corresponding carboxylic acid (white solid, 93% yield) .