The present invention relates to novel bicyclic nucleosides and oligomers prepared therefrom. In particular, the present invention relates to a compound of formula (I), wherein one of T1 and T2 is OR1 or OR2； and the other of T1 and T2 is OR1 or OR2； wherein R1 is H or a hydroxyl protecting group, and R2 is a phosphorus moiety； and wherein Bx is a nucleobase. Furthermore, the present invention relates to said compounds, bicyclic nucleosides and said oligomers for use as a medicament in the prevention, treatment or diagnosis of a disease.
