The present invention provides a novel methane-sulfonate salt of 3-(8-pentylamino)-2-methyl-(2-chloro-4-methoxyphenyl)-6, 7-dihydro-5H-cyclopenta[d]pyrazo[1, 5-a]pyrimidine, a crystal thereof, a process of preparing said salt and a process of preparing its synthetic intermediate.3-(8-pentylamino)-2-methyl-(2-chloro-4-methoxy-phenyl) -6, 7-dihydro-5H-cyclopenta[d]pyrazo[1, 5-a]-pyrimidine methanesulfonate salt is a highly heat-stable compound. Also, its synthetic intermediates, namely the compounds of general formula (I): (wherein Ar represents optionally substituted benzene ring etc. R1 represents C1-8 alkyl, C2-8 alkenyl, C2-8 alkynyl etc.) can be prepared in high efficiency and in high yield by the novel process according to the present invention.
