| 摘要 |
The present invention is concerned with a novel process for the preparation of compounds of formula (I) wherein R<1>, R<2> and X are as defined in the specification, comprising cyclocarbonylation of a compound of formula (II) wherein R<1>, R<2>, R<3> and X are as defined in the specification, to produce a compound of formula (III) wherein R<1>, R<2>, R<4> and X are as defined in the specification, followed by saponification. |
