The present invention relates to 8-(3-pentylamino)-2-methyl-3-(2-chloro-4-methoxyphenyl)-6,7 -dihydro-5H-cyclopenta[d]pyrazolo[1,5-a]pyrimidine methanesulfonate, a crystal thereof, a process for the preparation thereof, and a process for the preparation of an intermediate. 8-(3-Pentylamino)-2-methyl-3-(2-chloro-4-methoxyphenyl)-6,7-dihydro-5H-cyclopenta[d]pyrazolo[1,5-a]pyrimidine methanesulfonate was a superior compound for thermal stability. Besides, the compound of formula (I) wherein Ar is benzene etc . which may be substituted by substituents, R 1 is C1-8 alkyl, C2-8 alkenyl, C2-8 alkynyl etc.； which was an intermediate, can be prepared in efficient high yield by the novel method of manufacture.
