Cone Calix[4]arenes with Orientable Glycosylthioureido Groups at the Upper Rim: An In-Depth Analysis of Their Symmetry Properties

The two glycodusters alpha- and beta-D-mannosylthioureidocalix[4]arenes 1 and 2 in the cone geometry have been submitted to a conformational investigation with the DFT approach at the standard B3LYP/6-31G(d) level and using a water continuum solvent model. After a reasoned choice of the level of calculation and the evaluation of the properties of the monomeric components of 1 and 2, the intrinsic conformational properties of cone calix[4]arenes with orientable groups at the upper rim were thoroughly analyzed. From the possible combinations of the directions that the groups may assume, 10 different geometries derive, all chiral. These geometries are interchangeable through two different processes, named breathing equilibrium and arrow rotation, that allow a dense network connection among them. When the modeling of whole macrocydes 1 and 2 was performed, a huge difference in their conformational behavior that heavily influences the presentation mode of their saccharidic moieties was found.