| 摘要 |
The present invention provides a process for the production of a compound of formula (I) or a salt thereof, wherein R is hydrogen, a straight, branched o r cyclic C1-C6 alkyl group or an aryl group which may optionally be substitute d. This process comprises: (a) reacting a compound of formula (II), with a compound of formula (III), wherein R is as defined above and X is a leaving group, in the presence of N, N-diisopropylethylamine.
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