The general procedure for the synthesis of 3-hydroxy-1,1-cyclobutanedicarboxylic acid-1,1-diethyl ester from 3-(benzyloxy)cyclobutane-1,1-dicarboxylic acid is as follows: 3-(benzyloxy)cyclobutane-1,1-dicarboxylic acid-diethyl ester (2 g) was dissolved in ethanol (EtOH, 100 ml), and 10% palladium/carbon (Pd/C, 400 mg, 20% equiv) was added. The reaction suspension was subjected to hydrogenation at room temperature overnight. Upon completion of the reaction, the solvent was removed by evaporation under reduced pressure to afford the product 3-hydroxy-1,1-cyclobutanedicarboxylic acid-1,1-diethyl ester (1.3 g, 91.5% yield). The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3) with the following chemical shifts: δ 2.44-2.49 (m, 2H), 2.85-2.90 (m, 2H), 4.35-4.37 (m, 1H), 4.21 (q, J=7.2 Hz, 4H), 1.26 (t, J=10.8 Hz, 6H).
