Synthesis, Properties, and NAD+-NADH-Type Redox Ability of 14-Substituted 1,3-Dimethyl-5,10-methanocycloundeca[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dionylium Tetrafluoroborates and Their Hydride Adducts

A synthesis of 14-substituted 1,3-dimethyl-5,10-methanocycloundeca[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dionylium tetrafluoroborates 11a,b+·BF4- was accomplished by the methylation of 5,10-methanocycloundeca[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dione derivatives with MeI and following anion-exchange reaction by treatment with 42% aq HBF4. Compound 11b+·BF4- was synthesized alternatively by the reaction of 1,6-methano[11]annulenylium tetrafluoroborate with 6-phenylamino-1,3-dimethyluracil and following oxidative cyclization reaction. Remarkable structural characteristics of 11a,b+ were clarified on inspection of the UV−vis and NMR spectral data as well as X-ray crystal analyses. The stability of cations 11a,b+ is expressed by the pKR+ values which were determined spectrophotometrically as 9.8 and 9.7, which are smaller by 1.4 and 1.2 pH units than those of the corresponding seven-membered ring cations, respectively; however, the values are larger by 3.6 and 3.5 pH units than that of the parent 1,6-meth...