Profiling
of eight stereoisomeric T. cruzi growth
inhibitors revealed vastly different in vitro properties such as solubility,
lipophilicity, pKa, and cell permeability
for two sets of four stereoisomers. Using computational chemistry
and NMR spectroscopy, we identified the formation of an intramolecular
NH→NR3 hydrogen bond in the set of stereoisomers
displaying lower solubility, higher lipophilicity, and higher cell
permeability. The intramolecular hydrogen bond resulted in a significant
pKa difference that accounts for the other
structure–property relationships. Application of this knowledge
could be of particular value to maintain the delicate balance of size,
solubility, and lipophilicity required for cell penetration and oral
administration for chemical probes or therapeutics with properties
at, or beyond, Lipinski’s rule of 5.