Modification of guanosine with cyanopropargylic alcohols

Guanosine has been modified with tertiary cyanopropargylic alcohols under mild conditions (1:1.1-2 molar ratio, K2CO3, DMF, 20-25 °C, 19-50 h) to simultaneously give two modifications. The first product (1:1 adduct) is formed by the stereoselective addition of the amide function of the purine ring to the triple bond (38-43% yields), and the second product is the 1:2 adduct, with a second molecule of cyanopropargylic alcohol having reacted with the two vicinal hydroxy groups of the ribose moiety to give a functionalized 1,3-dioxolane ring (29-50% yields).