Synthesis of Cy5-Labelled C5-Alkynyl-modified cytidine triphosphates via Sonogashira coupling for DNA labelling.

New applications of palladium-catalyzed Sonogashira-type cross-coupling reaction between C5-halogenated 2'-deoxycytidine-5'-monophosphate and novel cyanine dyes with a terminal alkyne group have been developed. The present methodology allows to synthesize of fluorescently labeled C5-nucleoside triphosphates with different acetylene linkers between the fluorophore and pyrimidine base in good to excellent yields under mild reaction conditions. Modified 2'-deoxycytidine-5'-triphosphates were shown to be good substrates for DNA polymerases and were incorporated into the DNA by polymerase chain reaction.