| 摘要 |
The present invention is to provide a process for preparing a synthetic intermediate of biotin which is industrially advantageous, and discloses a process for preparing a compound represented by the formula (I) : <CHEM> wherein R<1> and R<2> may be the same or different from each other, and each represents hydrogen atom, a benzyl group which may have a substituent(s) on the benzene ring, a benzhydryl group which may have a substituent(s) on the benzen ring, or a trityl group which may have a substituent(s) on the benzene ring, R<3> represents cyano group, carboxyl group, an alkoxycarbonyl group, an alkylthiocarbonyl group, or a carbamoyl group which may have a substituent, or a salt thereof which comprises subjecting a compound represented by the formula (II-a) : <CHEM> wherein the symbols have the same meanings as defined above, or a salt thereof to ring transformation.
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