| 摘要 |
The invention relates to a process of making a compound of formula (I), wherein R1, R2, R3 and R4, independently, are hydrogen, lower alkyl, lower alkenyl, cycloalkyl or phenyl unsubstituted or substituted by up to 3 substituents independently selected from lower alkyl, lower alkoxy, or halogen, or R1 and R2 taken together are an alkyldiyl group containing 2 to 5 carbon atoms optionally substituted by at least one lower alkyl group, and n is an integer of from 0 to 3, and, when R1 is different from R2, and/or when R3 is different from R4, enantiomers, diastereomers and racemates thereof, and salts thereof with pharmaceutically acceptable bases. The method comprises reacting a compound of formula (V) with a compound of formula (VI), wherein n is an integer of from 0 to 3 and HAL is halogen, to give a compound of formula (II), wherein R5 is lower alkyl and n is an integer of from 0 to 3, followed by reacting a compound of formula (II) with a compound of formula (III) to form a compound of formula (IV), wherein n is an integer of from 0 to 3; and converting a compound of formula (IV) to a compound of formula (I).
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