2 research outputs found
Ethynyl, 2‑Propynyl, and 3‑Butynyl C‑Phosphonate Analogues of Nucleoside Di- and Triphosphates: Synthesis and Reactivity in CuAAC
The
synthesis and reactivity of a novel class of clickable nucleotide
analogues containing a C-phosphonate subunit that has an alkyne group
at the terminal position of the oligophosphate chain are reported.
The C-phosphonate subunits were prepared by simple one- or two-step
procedures using commercially available reagents. Nucleotides were
prepared by MgCl<sub>2</sub>-catalyzed coupling reactions and then
subjected to CuAAC reactions with various azide compounds to afford
5′-γ-labeled nucleoside triphosphates in excellent yields
Probing the Nature of the Co(III) Ion in Corrins: Comparison of Reactions of Aquacyanocobyrinic Acid Heptamethyl Ester and Aquacyano-Stable Yellow Cobyrinic Acid Hexamethyl Ester with Neutral N‑Donor Ligands
Equilibrium constants (log <i>K</i>) for substitution
of coordinated H<sub>2</sub>O in aquacyanocobyrinic acid heptamethyl
ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic
acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs),
in which oxidation of the C5 carbon of the corrin interrupts the normal
delocalized system of corrins, by neutral N-donor ligands (ammonia,
ethanolamine, 2-methoxyethylamine, <i>N</i>-methylimidazole,
and 4-methylpyridine) have been determined spectrophotometrically
as a function of temperature. Log <i>K</i> values increase
with the basicity of the ligand, but a strong compensation effect
between Δ<i>H</i> and Δ<i>S</i> values
causes a leveling effect. The aliphatic amines with a harder donor
atom produce Δ<i>H</i> values that are more negative
in their reactions with ACSYCbs than with ACCbs, while the softer,
aromatic N donors produce more negative Δ<i>H</i> values
with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and
a quantum theory of atoms in molecules analysis of the electron density)
shows that complexes of the aliphatic amines with SYCbs produce shorter
and stronger Co–N bonds with less ionic character than the
Co–N bonds of these ligands with the cobester. Conversely,
the Co–N bond to the aromatic N donors is shorter, stronger,
and somewhat less ionic in the complexes of the cobester than in those
of the SYCbs. Therefore, the distinction between the harder CoÂ(III)
in ACSYCbs and softer CoÂ(III) in ACCbs, reported previously for anionic
ligands, is maintained for neutral N-donor ligands