To examine the nuanced differences of oxazole-and oxadiazole-containing heterobiaryl sequences, we prepared two structural mimics of mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Previous studies have shown that macrocyclic peptides with an LDT motif as part of a b-turn were able to mimic the structural features of MAdCAM-1 and act as an antagonist for the α4β7 integrin receptor. We prepared peptides 16a and 16b with LDT containing sequences placed so that the Leu residue would theoretically be located at position i of the b-turn (Figure ). Gratifyingly, both peptides did in fact display the predicted LDT containing b-turn with the Leu at position i. However, each peptide displayed a unique conformation. This can be visualized through MCM analysis in Figure . Peptide 16a occupies both positive and negative f/y space whereas 16b occupies only negative f/ y space. The large differences in amino acid dihedral angles can likely be attributed to the f -dihedral angle of the heterobiaryl linkage in both 16a and 16b. The relatively flat (f = 2.2 o ) of 16a is contrasted by the non-planar 16b (f = 38.0 o ). The differences in amino acid and heterobiaryl dihedral angles of 16a and 16b manifest themselves in the b-turn of the LDT motif with a Type II-b-turn in 16a and a Type I-b-turn in 16b. Further, we found that the relative polarity of either peptide could be controlled basedheterobiaryl-graft. We found that the relative reversedphase HPLC retention times of 16a and 16b differed by over 0.7 minutes on a 15-minute gradient (5.54 minutes and 6.29 minutes respectively). In other studies, relative reversed-phase HPLC retention times have proven to be a useful metric in determining the permeability of peptide macrocycles, as longer retention times typically equate to lower aqueous solubility, lower polarity and increased lipophilicity. This suggest that, despite possessing a similar conformation to 16a, the oxazole heterobiaryl 16b is noticeably more non-polar and likely lipophilic when compared to oxadiazole heterobiaryl 16a.