We report the first example of alkylation of underivatized xanthine with chloroacetic acid to yield a separable mixture of N 7 -and N 9 -(methylenecarboxyl)xanthine and its conversion to a peptide nucleic acid monomer compatible with Fmoc-based oligomerization chemistry. Additionally, we have simultaneously prepared the N 7 -and N 9 -PNA monomers of guanine by alkylation of 2-N-isobutyrylguanine which were subsequently separated. Molecular modeling of the nucleobase base triplets indicates that N 7 -xanthine and N 7 -guanine form isomorphous triplets with adenine and guanine, respectively. We also show that polyamides containing N 7 -xanthine are compatible with triple-helix formation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.