Benzyl Bromide → 2-(S)-Hydroxy-3-(cyclopentyl)propanoic acid, benzyl ester

A solution of 287 mg (1.81 mmol) of 2-(S)-hydroxy-3-(cyclopentyl)propanoic acid (from Step F) in 8 mL of DMF was treated with 0.38 mL (2.72 mmol) of TEA and 0.33 mL (2.77 mmol) of benzyl bromide and stirred at rt for 22 h. The reaction was diluted with 200 ml of ether and washed with 200 mL of H2O, 200 mL of 2.0 N HCl, 200 mL of 1.0 N NaHCO3, 200 mL of H2O and 200 mL of sat'd NaCl. The organic layer was dried over MgSO4 and concentrated. Flash chromatography on silica gel using 17:3 v/v hexanes/EtOAc afforded 102 mg (22%, 95.5% ee) of the title compound: RF: 0.40 (4:1 v/v hexanes/EtOAc); 1H NMR (300 MHz): δ 1.04-1.17 (m, 2H), 1.46-1.87 (m, 8H), 1.99 (m, 1H), 2.65 (m, 1H), 4.22 (dd, J=7.8, 4.8, 1H), 5.23 (ABq, J=12.3, 2H), 7.32-7.41 (m, 5H). HPLC: Chirapak AS 4.6×250 mm column, 17:3 v/v hexanes/iPrOH, 0.5 mL/min, 220 nm. Retention times: (S)-Enantiomer, 12.2 min; (R)-enantiomer, 15.3 min.