| 摘要 |
A method for producing a compound represented by the general formula (I-A) or the general formula (I-B), comprising the following step: wherein R<1 >is an optionally substituted lower alkyl, and the like; R<2 >is a lower alkyl or an optionally substituted aralkyl, and the like; R<3 >is a lower alkyl, characterized in that a compound represented by the general formula (II-A) or the general formula(II-B) is treated with thionyl chloride.
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