Tautomerism, protonation, and ionization of formycin in aqueous solution by the ph dependence of 13c chemical shifts and 13c-1h coupling constants
Date of Original Version
Analyses of the pH dependence of 13C chemical shifts and 13C-1H coupling constants of formycin in aqueous solution revealed two pKa’s, at 4.4 and 9.7, corresponding to a protonation at N4 and an ionization at N1. The N4-protonation results in the transfer of a pyrazolo ring hydrogen from N1 to N2. At physiological pH, formycin was found to exist as a mixture of N1H and N2H tautomers, with the former being predominant (>94%). © 1994, Taylor & Francis Group, LLC. All rights reserved.
Nucleosides and Nucleotides
Cho, Bongsup P., and Michael A. Mcgregor. "Tautomerism, protonation, and ionization of formycin in aqueous solution by the ph dependence of 13c chemical shifts and 13c-1h coupling constants." Nucleosides and Nucleotides 13, 1-3 (1994): 481-490. doi:10.1080/15257779408013256.