| 摘要 |
A compound of the formula (1): wherein R<1 >and R<2 >are the same or different and represent a hydrogen atom, a hydroxyl protecting group, a phosphate group, or -P(R<3>)R<4>, wherein R<3 >and R<4 >are the same or different and represent a hydroxyl group, an amino group, an alkoxy group having from 1 to 4 carbon atoms, a cyanoalkoxy group having from 1 to 5 carbon atoms or an amino group substituted by an alkyl group having from 1 to 4 carbon atoms; A represents an alkylene group having from 1 to 4 carbon atoms and B represents a purin-9-yl group, a 2-oxo-pyrimidin-1-yl group, a substituted purin-9-yl group or a substituted 2-oxo-pyrimidin-1-yl group having a substituent alpha selected from the group consisting of a hydroxyl group which may be protected, an alkoxy group having from 1 to 4 carbon atoms, a mercapto group which may be protected, an alkylthio group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an amino group which may be protected, a mono- or di-alkylamino group which may be substituted by an alkyl group having from 1 to 4 carbon atoms, an alkyl group having from 1 to 4 carbon atoms and a halogen atom; or a salt thereof.
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