. . . "For example, such ribose modification at the 2???-position includes for example modifications by substituting the hydroxyl group at the 2???-position in ribose with H, OR1, R1, R2OR1, SH, SR1, NH2, NHR1, N(R1)2, N3, CN, F, Cl, Br and I. Herein, R1 represents alkyl or aryl." .