Irradiation of 4-(2-tetrahydropyranyloxy)-2-cyclopentenyl 3-acetoxyacrylate (2___∼) resulted only in an E___--Z___- isomerization. Also, the corresponding 4-oxo-2-cyclopentenyl derivative (7___∼) did not give the cyclized product on irradiation. These facts clearly indicate that the Libit's method is only an idea without any experimental verification.