Absolute structure and structure-function relationships of 4R,2′R and 4S,2′S Pidotimod®

The molecular and crystal structures of the 4R,2′R and 4S,2′S Pidotimod® stereoisomers here presented gave some hints on the differences in bioactivity with respect to the 4R,2′S stereoisomer. In fact, beyond an expected different dispositions of hydrophilic ligands, 4R,2′R and 4S,2′S showed an incremented tendency to intermolecular H-bonds with water.