The present invention relates to an enantiomerically pure (+)-trans enantiomer of a compound represented by the following formula (I): wherein R1, R2, R3, R4 and R9 are as defined in the specification； enantiomerically pure intermediates thereof, to processes for the preparation of the enantiomerically pure compound and its intermediates, and to a pharmaceutical composition comprising the enantiomerically pure compound. The compound of formula (I) is useful for the treatment of diseases or disorders mediated by the inhibition of cyclin dependant kinase, such as cancer.
