A process for the preparation of a compound of formula (I) or a pharmaceutically acceptable salt thereof: ##STR1## wherein R.sub.1 represents ##STR2## in which r represents an integer of 2 to 4, s represents 1 or 2 and t represents 0 or 1; R.sub.2 is a group OR.sub.4, where R.sub.4 is C.sub.1-4 alkyl, C.sub.2-4 alkenyl or C.sub.2-4 alkynyl or a group OCOR.sub.5 where R.sub.5 is hydrogen or R.sub.4 ; and R.sub.3 is CN; said process comprising reacting a compound of formula (II): ##STR3## wherein R.sub.1 ' is R.sub.1 or a group convertible thereto, and R.sub.3 ' is an electron withdrawing group, with a source of nitrous acid, and thereafter converting the resulting .dbd.NOH group to .dbd.NR.sub.2 wherein R.sub.2 is as defined in formula (I), converting R.sub.1 ' and R.sub.3 ' when other than R.sub.1 and R.sub.3 to R.sub.1 and R.sub.3, and thereafter optionally forming a pharmaceutically acceptable salt.
一种制备化合物的方法,该化合物的结构式为(I)或其药学上可接受的盐:其中R.sub.1代表##STR2##其中r表示2至4之间的整数,s表示1或2,t表示0或1;R.sub.2是一个基团OR.sub.4,其中R.sub.4是C.sub.1-4烷基,C.sub.2-4烯基或C.sub.2-4炔基,或者是一个基团OCOR.sub.5,其中R.sub.5是氢或R.sub.4;R.sub.3是CN;所述方法包括将化合物(II)与
硝酸源反应,然后将生成的.dbd.NOH基团转化为.dbd.NR.sub.2,其中R.sub.2如公式(I)中定义,将R.sub.1'和R.sub.3'转化为R.sub.1和R.sub.3(除R.sub.1和R.sub.3之外),然后可选择形成药学上可接受的盐。