Late-Stage Functionalization\nof Guanine-Based Nucleosides,\nNucleotides, and Oligonucleotide: Synthesis and Derivatization of\nTricyclic Nucleoside Analogues

We report here the synthesis of tricyclic nucleoside\nanalogues\nvia acid-catalyzed cyclization of guanine with 1,1,3,3-tetramethoxypropane.\nThe method enables the use of hydroxyl-unprotected antiviral drugs\n(acyclovir, ganciclovir, and penciclovir), guanosines, oligonucleotide,\nand triazole-linked nucleoside dimers as substrates. Nucleoside trimer\nand tetramer were synthesized by derivatization reactions.