jo301008c_si_002.pdf (2.95 MB)
Conformational Analysis of a Model Synthetic Prodiginine
journal contribution
posted on 2012-08-03, 00:00 authored by María García-Valverde, Ignacio Alfonso, David Quiñonero, Roberto QuesadaA conformational analysis of a synthetic model prodiginine
was
carried out. In solution this compound showed a strong preference
for the β conformation, in which all the heterocycles are mutually
cis. This conformation provided an ideal alignment of the three N–H
groups for interacting with anions when the molecule is protonated.
A different conformation was also detected in d6-DMSO for the mesylate salt, assigned to the α conformation,
in which the C ring is engaged in an intramolecular hydrogen bond
with the OMe group. The formation of a homodimer was observed in concentrated
CDCl3 solutions of the neutral free base form of this prodiginine
derivative. DFT calculations and the solid state structures of the
hydrochloric and methanesulfonic acid salts were in good agreement
with the results observed in solution. A complete study of the relative
energies of different tautomers, isomers, and supramolecular complexes
supported the preference for the β conformation both in water
and in the gas phase.