Patent ID: 7615619

Claim:
A compound of the following general formula (1) or a salt thereof: wherein A represents a direct bond or —O—(CH2)— (wherein an oxygen atom is linked to a methylene group at the 4′-position) B represents a purin-9-yl group, a 2-oxo-pyrimidin-1-yl group, or a purin-9-yl group or a 2-oxo-pyrimidin-1-yl group which has a substituent selected from the following α group: α group: a hydroxyl group, a hydroxyl group protected with a protective group for synthesis of nucleic acid, an alkoxy group having 1 to 5 carbon atoms, a mercapto group, mercapto group protected with a protective group for synthesis of nucleic acid, an alkylthio group having 1 to 5 carbon atoms, an amino group, an amino group protected with a protective group for synthesis of nucleic acid, an amino group substituted by an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms, and a halogen atom, R 1 and R 2 are identical or different, and each represents a hydrogen atom, a protective group for an amino group for synthesis of nucleic acid, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, an acyl group, a silyl group —P(O) (R 7 )R 8 or —P(R 7 )R 8 where R 7 and R 8 are identical or different, and each represents a hydroxyl group, a hydroxyl group protected with a protective group for synthesis of nucleic acid, a mercapto group, a mercapto group protected with a protective group for synthesis of nucleic acid, an amino group, an alkoxy group having 1 to 5 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, a cyanoalkoxy group having 1 to 6 carbon atoms, or an amino group substituted by an alkyl group having 1 to 5 carbon atoms, and R 3 represents a hydrogen atom, aliphatic acyl group, an aromatic acyl group, a methyl group substituted by 1 to 3 aryl groups, a methyl group substituted by 1 to 3 aryl groups, with aryl rings being substituted by a lower alkyl, lower alkoxy, halogen or cyano group, a silyl group, a phosphoroamidite group, or —P(O) (R 7 )R 8 .