General procedure for the synthesis of ethyl 3-hydroxycyclobutanecarboxylate from ethyl 3-oxocyclobutanecarboxylate: to a solution of ethyl 3-oxocyclobutanecarboxylate (0.18 g, 1.27 mmol) in methanol (10 mL) was slowly added sodium borohydride (0.048 g, 1.27 mmol) at 0 °C. The reaction mixture was stirred continuously at 0 °C for 30 min, followed by quenching the reaction with aqueous 1N hydrochloric acid. Volatile solvents were removed by distillation under reduced pressure and the residue was extracted by partitioning with ethyl acetate and 1N aqueous hydrochloric acid. The organic phase was dried over anhydrous magnesium sulfate and concentrated under reduced pressure to afford the target product ethyl 3-hydroxycyclobutanecarboxylate (0.17 g, 93% yield) as a mixture of cis and trans isomers. The product was characterized by 1H NMR (500 MHz, CDCl3), δ 4.17-4.24 (m, 1H), 4.15 (d, J=7.2 Hz, 2H), 2.54-2.66 (m, 3H), 2.11-2.22 (m, 2H), 1.27 (t, J=7.2 Hz, 3H).
