Table 1.

Initial studies at determining optimal conditions for synthesis of the O⁶-(benzotriazol-1-yl)guanosine analogues 3 and 4^a

Entry	Substrate	Solvent	Base	Temp	Time	Yieldb
1	1	DMSO	i-Pr2NEt	55 °C	24 h	54%
2	1	THF	i-Pr2NEt	rt	96 h	NRc
3	1	THF	DBU	rt	4 h	45%
4	1	CH3CN	DBU	rt	2 h	65%
5	2	CH3CN	DBU	rt	1 h	85%

^aReactions were performed using 2.0 molar equiv each of BOP and DBU at ~0.1 M nucleoside concentration.

^bWhere reported, yield is of isolated and purified products.

^cNo reaction was observed and only 1 was present.