Substituent Effects on the Basicity of Patriscabrin A and Lettucenin A: Evolution Favors the Aromatic?

Basicities for derivatives of patriscabrin A and lettucenin A were calculated with density functional theory. A significant correlation is observed between the basicity and Hammett σ parameters. Protonation increases the aromatic character of the cyclic moieties of each natural product. The naturally occurring structures are predicted to be the most aromatic.