Patent ID: 7485717

Claim:
A method of preparing an adenosine, guanosine or cytidine monomer having a protected nucleoside base and a protected 3′-amino group, wherein said base and said 3′-amino group are orthogonally protected, the method comprising: (a) providing a 3′-amino-3′-deoxy adenosine, cytidine, or guanosine monomer in which the 5′-hydroxyl group, nucleoside base, and 3′-amino group are unprotected; (b) selectively reacting said 3′-amino group with a first protecting group consisting of a triarylmethyl group or fluoroenylmethoxycarbonyl group; (c) reacting said 5′-hydroxyl group of the compound from step (b) with a second protecting group consisting of acyl, base-labile trialkyl silyl ether, or fluoride-labile silyl ether; and (d) reacting said nucleoside base of the compound from step (c) with a third protecting group consisting of an acyl group or a formamidinyl group; wherein said first protecting group can be removed from said 3′-amino group, under conditions which do not deprotect said nucleoside base, and said second protecting group can be removed from said 5′-hydroxyl group under conditions which do not deprotect said nucleoside base or said 3′-amino group.