The tautomerism of 2'-deoxy-7-deaza-isoguanosine (2) was studied and compared to that of 2'-deoxyisoguanosine (1). The fixed (1)N-methyl (8) and O-methyl (4) derivatives were synthesized to represent the pure extremes of each tautomer. The replacement of the imidazole ring in 1 with a pyrrole ring in 2 makes the keto form in the latter more favored by 2 orders of magnitude (K(TAUT) for 2 approx...

In the title compound, C(15)H(15)N(5)O(2), the nitro O atoms are disordered over two sets of sites with an occupancy ratio of 0.75 (4):0.25 (4). Amine-imine tautomerism is observed in the formazan group. This was evident from the similar C-N bond distances in the formazan [1.319 (2) and 1.332 (3) Å], as well as the distribution of the imine proton in the Fourier difference map which refined to ...

A. S. Shawali, M. A . A bdallah , and M. E. M. Z ay ed Department of Chemistry, Faculty of Science, University of Cairo, Giza, Egypt Reprint requests to Dr. A. S. Shawali. E-mail: [email protected] Z. Naturforsch. 55b, 546-552 (2000); received February 4. 2000 Ring-Chain Tautomerism. Heterocyclic Ring Transformation, 1,3,4-Thiadiazoles The synthesis and antimicrobial activity of a s...

2,6-Bis(2-quinolyl)-4(1H)-pyridone 1, a novel quinoline analogue of the well-known ligand 2-terpyridone, shows unusual fluorescence with a large Stokes shift and low energy emission. Pyridine-pyridone tautomerism is investigated by NMR and theoretical methods and indicates that the low energy emission is from the pyridine form. 1 reacts with Ag(i) salts to give a double helical Ag2N6 core showi...

In this laboratory exercise we will measure a chemical equilibrium constant using key proton signals in a Nuclear Magnetic Resonance (NMR) spectrum. Those doing the “traditional” P Chem experiments will examine a keto-enol tautomerism, while those doing the “biophysical” experiments will look at the cis-trans equilibrium for a peptide bond. In each case, the relative concentration of the equili...