Monocyclic Heterocyclic Biomolecules Conform to the Rule of Topological Charge Stabilization

Abstract

Abstract Some difficulty is felt in applying the rule of topological charge stabilization (TCS rule) to monocyclic heterocyclic biomolecules, such as substituted pyrroles, furans, thiophenes, imidazoles, and thiazoles. We found that the TCS rule can be reasonably extended to include such heterocycles. We propose that, if all carbon atoms in a hydrocarbon anion are charged uniformly, one or more of them can be replaced by eletronegative heteroatoms to stabilize the π-electron system. Thus, it is still true that the TCS rule dominates general biosynthesis and geochemistry. Coenzyme PQQ (pyrroloquinolinequinone) satisfies the TCS rule in both its oxidized and reduced states. Even apparently antiaromatic 1,2-dithiin seems to conform to the TCS rule.