| abstract |
In this method, an oligonucleotide represented by formula (II) [wherein Y 1 , Q, Base, r and r′ are each as defined in claim 1 ] is prepared by using, as a synthesis unit, a novel nucleoside monomer compound represented by formula (I) [wherein X, R 1 , Y, Base, Z, Ar, R 2 , R 3 and n are each as defined in claim 1 ]. The novel nucleoside monomer compound is a nucleoside, the base moiety of which is substituted with an aromatic-hydrocarbon-ring-carbonyl or -thiocarbonyl group having at least one hydrophobic group. The method can dispense with column-chromatographic purification in every reaction, and enables base elongation not only in the 3′-direction but also in the 5′-direction, thus attaining efficient liquid-phase mass synthesis of an oligonucleotide. |