Synthesis and Antitumor Activity of C-7-Alkynylated and Arylated Pyrrolotriazine C-Ribonucleosides

A number of biologically active nucleoside analogues contain the adenine isostere 4-amino-pyrrolo[2,1-f][1,2,4]triazine connected to various sugar moieties through a C-C anomeric linkage. We employed palladium-catalyzed cross-coupling chemistry to promptly functionalize the 7-position of such a heterocyclic scaffold with various alkynyl and aryl groups starting from a common 7-iodo-pyrrolotriazine C-ribonucleoside intermediate. Analogues bearing a 7-cyclopropyl-, 7-propyl-, and 7-butylacetylene moiety displayed potent cytotoxic activity, with the latest being the most selective of this series toward cancer cells. Further insights revealed that such C-nucleosides could exert their antiproliferative action by causing dose-dependent DNA damage.