Water → (S)-a-Hydroxy-cyclobutanepropanoic acid

A suspension of 33.66 g (0.3 mol) of potassium t-butoxide in 50 mL of THF was treated with 5.40 mL (0.3 mol) of H2O. The resulting mixture was treated with a solution of 11.48 g (0.061 mol) of N-methyl-N-methoxy 2-(S)-hydroxy-3-cyclobutyl propanamide (from Step C) in 20 mL of THF and stirred at rt for 20 h. The mixture was concentrated and the residue was partitioned between 300 mL of ether and 200 mL of H2O and the layers were separated. The pH of the aqueous layer was adjusted to 2 with concentrated HCl and extracted with 300 mL of EtOAc. The extract was washed with 100 mL of sat'd NaCl, dried over MgSO4 and concentrated to afford 7.50 g (85%) of the title compound: 1H NMR (500 MHz) δ 1.66-1.76 (m, 2H), 1.78-1.98 (4H), 2.06-2.16 (m, 2H), 2.51-2.61 (m, 1H), 4.20 (dd, J=8.0, 4.0, 1H).