Pyridinio‐isoalloxazinophanes as Model Systems for Active‐Site Complexes in Flavoenzymes: Syntheses, X‐Ray Structure Analyses and Spectroscopic Properties

As model systems for active site complexes in flavoenzymes, flavin and nicotinamide analogues were linked together in cyclophane skeletons of specific sterical structures. Elaborating this concept, we prepared [4]metacyclo[3](10,6)isoalloxazinophane ( 3 ), [4](3,1)pyridino[3](10,6)isoalloxazinophane ( 4 ), as well as the 16‐methoxycarbonyl and the 16‐carboxylato derivatives ( 2 and 34 , resp.), of 4 by multistep syntheses. For the isoalloxazinophanes 2 , 3 , 4 , and 34 X‐ray structure analyses were performed and are discussed with regard to intramolecular interactions. Preliminary UV/Vis‐spectroscopic results related to π…π interactions in these isoalloxazinophanes are reported.