The reaction sequence is represented by the following reaction scheme. 5th 3 N step R are: 5th step 6th N step l n u H z H 4' a. step 114 ,JZl J RI gllth RI step I R N N H i R H R H (X) (I1) (wherein R is a hydrogen atom or a lower alkyl group, e.g. methyl, ethyl, propyl, butyl; R and R are the same or different and each is a hydrogen atom or a lower alkoxy group, e.g. methoxy, ethoxy, propoxy; X