NEW MATERIAL:A 2-substituted-3-hydroxy-3-methyl-4-cyclopentenone expressed by formulaI(R is 2-pentynyl, 2-cis-pentenyl, 2-trans-pentenyl or 2,4-cis-pentadienyl).

EXAMPLE: 2-(2-PentynyL)-3-hydroxy-3-methyl-4-cyclopentenone.

USE: A synthetic raw material for cis-jasmone and a syntheti intermediate for cis-jasmones or an intermediate for agricultural chemicals.

PROCESS: A furancarbinol derivative expressed by formula II is adjustd to a pH of 3.5W6.5 in a solvent consisting of water essentially with excess water solvent, potassium monohydrogenphosphate-phosphoric acid, etc., and then rearranged in the presence or abesence of a catalyst, e.g. tetrabutylammonium bromide, at 20W160°C to give the compound expressed by formulaIin high yield.