| 摘要 |
<p>A process for the preparation of a compound of formula (I) or a pharmaceutically acceptable salt thereof wherein R1 represents (a) in which r represents an integer of 2 to 4, s represents 1 or 2 and t represents 0 or 1; R2 is a group OR4, where R4 is C1-4alkyl, C2-4alkenyl or C2-4alkynyl or a group OCOR5 where R5 is hydrogen or R4; and R3 is CN; said process comprising reacting a compound of formula (II) wherein R1' is R1 or a group convertible thereto, and R3' is an electron withdrawing group, with a source of nitrous acid, and thereafter converting the resulting =NOH group to =NR2 wherein R2 is as defined in formula (I), converting R1' and R3' when other than R1 and R3 to R1 and R3, and thereafter optionally forming a pharmaceutically acceptable salt.</p> |
