1H and 13C NMR signal assignments of some new N,N'-diacyl proflavine derivatives

The complete 1H and 13C NMR signal assignments of 23 new N,N'-diacyl proflavine derivatives were achieved using one- and two-dimensional experiments (DEPT, HMQC and HMBC).

Differentiation of heterocyclic regioisomers: a combined tandem mass spectrometry and computational study of N-acridin-4-ylbenzylamide and N-acridin-2-yl-benzylamide

Electrospray ionization (ESI) tandem mass spectrometry (MS/MS) has been used to differentiate two positional isomers of acridine derivatives, N-acridin-4-ylbenzylamide and N-acridin-2-ylbenzylamide. The study revealed that the isomeric ion structures produced by these heterocycles could be distinguished upon collision-induced dissociations (CID). In particular, the loss of a water molecule was shown to be a regiospecific reaction of the protonated N-acridin-4-ylbenzylamide, in which the location of the benzylamide substituent with respect to the acridinic nitrogen greatly assists proton migration by allowing the creation of intramolecular hydrogen bonds. To a lesser extent, the two isomers could also be distinguished by the difference in the abundance of the benzoyl cation in the MS/MS spectra of the [M+H]+ ions, as this ion is produced with a much higher rate from N-acridin-4-ylbenzylamide. Calculations based on quantum-mechanical models have been performed to evaluate the stability of the ion structures and to support mechanisms proposed for these two dissociation reactions.