Abstract: Novel nucleotide compounds represented by the formula (I) wherein R1 represents a protective group or a PEG bearing organic group; R2, R2′, R2″, R3, R3′ and R3″ each represents a hydrogen atom or an alkyl, cycloalkyl, aryl or aralkyl group which may contain a hetero-atom; B1, B2, B3 and B4 each represents a base, if necessary, protected by a protective group common in nucleotide chemistry or by a PEG bearing organic group; X, X′ and X″ each represents an oxygen atom or a sulfur atom; Y represents an azolyl group, a mono- or di-alkylamino group or a saturated nitrogenous heterocyclic ring; A1, A2, A3 and A4 each represents a hydrogen atom, a hydroxyl group, an alkoxy group or a trialkylsilyloxy group; and m and n each represents 0 or an integer of 1 to 100.