Chiral Cyclobutane-Based Ureas as Versatile Platforms to Tune Structural Diversity: An Experimental and Theoretical Approach

Four new chiral 2,2′-disubstituted biscyclobutane ureas have been synthesized and crystallized. Each of them bears a different substituent on positions 2,2′, that is, esters, hydroxymethyl groups, and carboxyl groups. The mode of aggregation of each urea in the crystal packing to form chains, helices, sheets, and others is tuned both by the intermolecular hydrogen bonds between the urea groups and by the different ability of the substituents to generate extra hydrogen bonding. Experimental results have been rationalized with the aid of computational calculations, which allow to understand the contribution of the energetic factors to the stabilization of the preferential structures observed.