Dialkyl 2-phenylfuran (and 2-phenyltetrahydrofuran)-3,4-dicarboxylates (1, 2, 5-7), which are potential precursors of the synthesis of furofuran and tetrahydrofurofuran lignans, can be selectively hydrolyzed to monoacid (3, 8) by potassium hydroxide. The regioselective hydrolysis was affected significantly by the 2-phenyl group of the furan or tetrahydrofuran skeleton. The geometric structures of 3, 8 and related compounds were elucidated and verified by NMR spectra. Dialkyl 2-phenylfuran (and 2-phenyltetrahydrofuran) -3,4-dicarboxylates (1,2, 5-7), which are potential precursors of the synthesis of furofuran and tetrahydrofurofuran lignans, can be selectively hydrolyzed to monoacid (3, 8) by potassium hydroxide. The regioselective hydrolysis was affected significantly by the 2-phenyl group of the furan or tetrahydrofuran skeleton. The geometric structures of 3, 8 and related compounds were elucidated and verified by NMR spectra.