PROBLEM TO BE SOLVED: To provideC labeled isoquinoline derivatives labeled with [C] methyl group on isoquinoline ring present in fasudil, analogs thereof which are Rho kinase inhibitors, and preparation method therefor and precursors suitably used in preparation of theC labeled isoquinoline derivatives.SOLUTION: There are exemplified, (S)-hexahydro-2-methyl-1-[(4-[C] methyl-5-isoquinolinyl)sulfonyl]-1H-1,4-diazepine, etc., as theC labeled isoquinoline derivatives. The compounds are obtained in a short time by using precursors having protective groups such as a trihaloacetyl group, after introducing a [C] methyl group onto the isoquinoline ring of the precursors, removing the protective group under a basic condition. The compounds can be suitably used as an imaging agent in imaging a tissue by using PET method, etc.
