Oxetanes display properties comparable to ketone carbonyl groups and are increasingly explored as bioisosteres. However, does the comparison hold for the most common carbonyl derivatives: do amino-oxetanes resemble amides? Here, we present a matched molecular pair study of 12 3-aryl-3-amino-oxetane and benzamide matched molecular pairs to assess their viability as isosteres. Across the surveyed physicochemical properties (pH stability, solubility, lipophilicity, clearance, permeability), amino-oxetanes exhibited broadly comparable profiles to their amide counterparts. Amino-oxetanes maintain both the H-bond acceptor and H-bond donor capabilities of analogous amides. These findings support the potential of amino-oxetanes as amide replacements. However, crystal structure analysis highlights the conformational differences and alternative exit vectors available through introduction of the oxetane ring. The preferred gauche conformation makes the torsion angle and exit vectors of amino-oxetanes more similar to sulfonamides, and therefore better like-for-like topological replacements. Overall, amino-oxetanes present an attractive design option to modulate physicochemical properties and chemical topology.
Ishikura et al. (Wed,) studied this question.