Crystallographic analysis. Next, we compared the geometric parameters of 2-oxabicyclo[2.1.1]hexanes with the orthosubstituted phenyl ring and their previously suggested saturated bioisosteres, bicyclo [1.1.1]pentanes and bicyclo [2.1.1]heptanes. For that, we employed the exit vector plots tool. In this method, substituents at the disubstituted scaffold were simulated by two exit vectors n1 and n2 (Figure ). The relative spatial arrangement of vectors is described by four geometric parameters: the distance between C-variation atoms r, the plane angles 1 (between vectors n1 and C-atom) and 2 (between n2 and C-atom), and the dihedral angle  defined by vectors n1, CC and n2. An additional important parameter -distance d between two carbon substituents (Figure ) -was also measured.