Main Group Pentafulvenes: Challenges and Opportunities in Heavy Main Group Isolobal Substitution of Pentafulvene

Heterofulvenes based on isolobal substitution of carbon fragments by (heavier) main group motifs provide a rich source of structurally interesting building blocks with electronic situations that can vastly differ from all-carbon congeners. Group 13, heavier 14 & 16 fulvenes are rare and pose significant stability challenges, while group 15 derivatives, particularly phosphorus and arsenic, have led to many derivatives with intriguing opto-electronic properties.

Synthesis and electrochemistry of 2-ethenyl and 2-ethanyl derivatives of 5-nitroimidazole and antimicrobial activity against Giardia lamblia

Infections with the diarrheagenic pathogen, Giardia lamblia, are commonly treated with the 5-nitroimidazole (5-NI) metronidazole (Mz), and yet treatment failures and Mz resistance occur. Using a panel of new 2-ethenyl and 2-ethanyl 5-NI derivatives, we found that compounds with a saturated bridge between the 5-NI core and a pendant ring system exhibited only modestly increased antigiardial activity and could not overcome Mz resistance. By contrast, olefins with a conjugated bridge connecting the core and a substituted phenyl or heterocyclic ring showed greatly increased antigiardial activity without toxicity, and several overcame Mz resistance and were more effective than Mz in a murine giardiasis model. Determination of the half-wave potential of the initial one-electron transfer by cyclic voltammetry revealed that easier redox activation correlated with greater antigiardial activity and capacity to overcome Mz resistance. These studies show the potential of combining systematic synthetic approaches with biological and electrochemical evaluations in developing improved 5-NI drugs.