The purine ring system is undoubtedly one of the most ubiquitous heterocyclic ring systems in nature as it has the distinction of being the parent ring in countless derivatives of biological relevance. It is not surprising then that modified purines possess the potential to impact several areas, including a better understanding of the biological effects of DNA damaging agents, enzyme/substrate interactions, and in the development of more potent medicinal agents. One focus for our research at Georgia Tech has centered around the design and synthesis of a series of extended purine analogues containing a heterocyclic spacer ring, with sites set on investigations into their use as (i) potential anticancer and antiviral agents, (ii) dimensional probes for enzyme and coenzyme binding sites, and (iii) structural probes of the minor groove of DNA. The synthesis and preliminary antitumor activity of two thieno-separated purine analogues are described herein. Tricyclic 1 was synthesized in 12 steps from tribromoimidazole and with an overall yield of 7%. Tricyclic 2 was synthesized in 9 steps with an overall yield of 13%. Both 1 and 2 exhibited growth inhibitory effects on HCT116 colorectal cancer cells in vitro.

Intramolecular C–H⋯F hydrogen bonding has been utilized to induce 1,2,3-triazole oligomers to fold into stable artificial secondary structures.

The synthesis of two flexible nucleosides is presented. The "fleximers" feature the purine ring system split into its imidazole and pyrimidine components. This modification serves to introduce flexibility to the nucleoside while still retaining the elements essential for molecular recognition. As a result, these structurally innovative nucleosides can more readily adapt to capricious binding sites and, as such, should find use for investigating enzyme-coenzyme as well as nucleic acid-protein interactions.

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