Fig. 4. (A–D) HPLC (radio-HPLC) chromatograms (for HPLC method, see ESI Table S2†) of analogues of [¹⁸F]6(DHP(a, b), DHP(a) and DHP(b)) after HPLC separation of the fractions for log D_7.4 evaluation, together with the (E) chemical structures of head-to-head and head-to-tail conformations of 1,4-DHPs.