NEW MATERIAL:A compound expressed by formula I [R is H, acyl or (substituted) phosphoryl; T is thymin-1-yl; Y1 to Y3 are H, OH or lower alkyloxy, etc.; B is thymin-1-yl, adenin-9-yl or guanin-9-yl, etc.; n is 1-100].

USE: Carrier for isolating poly(A)+-mRNA. Useful for promotion of efficiency in isolation of poly(A)+-mRNA as forming stable hybrid with poly(A) part.

PREPARATION: The aimed substance is synthesized from nucleotide derivative expressed by formula II (X is monomethoxytrityl or dimethoxytrityl, etc.; Y is H or o-chlorophenyl phosphoric acid, etc.) using, e.g. DNA automatic synthesizer. Besides, the compound expressed by formula II is new substance and obtained from, e.g. ribothymidine as starting raw material through compounds expressed by formula III and formula IV.