3 research outputs found
Tunable Heck–Mizoroki Reaction of Dibromonaphthalene Diimide with Aryl Ethylenes: Design, Synthesis, and Characterization of Coplanar NDI-Based Conjugated Molecules
Rational
design of coplanar NDI-based conjugated molecules was
achieved by covalently connecting naphthalene diimide (NDI) units
with aryl (Ar) groups through vinylene (V) linkers via Heck–Mizoroki
reaction. Two series of products, diolefination products (Ar<i>V</i>NDI<i>V</i>Ar) and hydroxylated and mono-olefination
products (HONDI<i>V</i>Ar), can be obtained, respectively,
in moderate to excellent yields (45–90%) under controlled conditions,
in which catalyst and base play the key roles. Density functional
theory calculation discloses the outstanding planarity of the two
types of products. Large bathochromic shifts are observed in both
the absorbance and photoluminescence spectra of the HONDI<i>V</i>Ar (144 and 229 nm) and Ar<i>V</i>NDI<i>V</i>Ar (180 and 242 nm) π-systems. Bathochromic shifts can be adjusted
within the broad wavelength range by introducing 4′-substituents,
either electron-withdrawing group (NO<sub>2</sub>) or electron-donating
group (NMe<sub>2</sub>), in the phenyl group of aryl ethylenes. Ar<i>V</i>NDI<i>V</i>Ars show bigger bathochromic shifts
than HONDI<i>V</i>Ars
Palladium-Catalyzed Alkynylation of Morita–Baylis–Hillman Carbonates with (Triisopropylsilyl)acetylene on Water
Direct
alkynylation of Morita–Baylis–Hillman carbonates with
(triisopropylsilyl)Âacetylene catalyzed by a PdÂ(OAc)<sub>2</sub>–NHC
complex was developed “on water” to give the corresponding
1,4-enynes. The significant effects of water amount in the solvent
on further transformations of 1,4-enynes were investigated
Consequences of Depsipeptide Substitution on the ClpP Activation Activity of Antibacterial Acyldepsipeptides
The acyldepsipeptide
(ADEP) antibiotics operate through a clinically
unexploited mechanism of action and thus have attracted attention
from several antibacterial development groups. The ADEP scaffold is
synthetically tractable, and deep-seated modifications have produced
extremely potent antibacterial leads against Gram-positive pathogens.
Although newly identified ADEP analogs demonstrate remarkable antibacterial
activity against bacterial isolates and in mouse models of bacterial
infections, stability issues pertaining to the depsipeptide core remain.
To date, no study has been reported on the natural ADEP scaffold that
evaluates the sole importance of the macrocyclic linkage on target
engagement, molecular conformation, and bioactivity. To address this
gap in ADEP structure–activity relationships, we synthesized
three ADEP analogs that only differ in the linkage motif (i.e., ester,
amide, and <i>N</i>-methyl amide) and provide a side-by-side
comparison of conformational behavior and biological activity. We
demonstrate that while replacement of the naturally occurring ester
linkage with a secondary amide maintains <i>in vitro</i> biochemical activity, this simple substitution results in a significant
drop in whole-cell activity. This study provides direct evidence that
ester to amide linkage substitution is unlikely to provide a reasonable
solution for ADEP instability