Triazine Macrocycle Libraries: Synthesis, logD Prediction, and a Surprisingly Hydrophobic, Membrane-Permeable Diamine

A library of triazine macrocycles was obtained to evaluate strategies for predicting lipophilicity using additive algorithms. Two synthetic routes were examined. While both were successful, one proved amenable to solution-phase library synthesis. The octanol-water partition coefficients (logP) were measured using reverse-phase HPLC at pH 10. When experimental and computed values (AlogP) are compared, a linear correlation is observed. That is, while additive algorithms underestimate hydrophobicity by a factor of 100, a simple correction yields accurate predictions. Two macrocycles showed anomalous hydrophobicities at high pH that were borne out in membrane transit (PAMPA) studies. Homodimers containing two primary amines were more hydrophobic than the corresponding heterodimers containing a single amine and a hydrophobic group. Structural analysis and computation provide a rationale for this behavior: the amines engage in an intramolecular hydrogen bond.