Highly substituted polycyclic aromatic and heteroaromatic compounds are produced via a two-stage tandem benzannulation/cyclization strategy. The initial benzannulation step proceeds via a pericyclic cascade mechanism triggered by thermal or photochemical Wolff rearrangement of a diazo ketone. The photochemical process can be performed using a continuous flow reactor which facilitates carrying out reactions on a large scale and minimizes the time required for photolysis. Carbomethoxy ynamides as well as more ketenophilic bissilyl ynamines and N-sulfonyl and N-phosphoryl ynamides serve as the reaction partner in the benzannulation step. In the second stage of the strategy, RCM generates benzofused nitrogen heterocycles, and various heterocyclization processes furnish highly substituted and polycyclic indoles of types that were not available by using the previous cyclobutenone-based version of the tandem strategy.
A two-stage “tandem strategy” for the synthesis of indoles with a high level of substitution on the six-membered ring is described. Benzannulation based on the reaction of cyclobutenones with ynamides proceeds via a cascade of four pericyclic reactions to produce multiply substituted aniline derivatives in which the position ortho to the nitrogen can bear a wide range of functionalized substituents. In the second stage of the tandem strategy, highly substituted indoles are generated via acid-, base-, and palladium-catalyzed cyclization and annulation processes.
Chemotherapy of bladder
cancer has limited efficacy because of
the short retention time of drugs in the bladder during therapy. In
this research, nanoparticles (NPs) with a new core/shell/corona nanostructure
have been synthesized, consisting of iron oxide (Fe3O4) as the core to providing magnetic properties, drug (doxorubicin)
loaded calcium phosphate (CaP) as the shell for pH-responsive release,
and arginylglycylaspartic acid (RGD)-containing peptide functionalized
alginate as the corona for cell targeting (with the composite denoted
as RGD-Fe3O4/CaP/Alg NPs). We have optimized
the reaction conditions to obtain RGD-Fe3O4/CaP/Alg
NPs with high biocompatibility and suitable particle size, surface
functionality, and drug loading/release behavior. The results indicate
that the RGD-Fe3O4/CaP/Alg NPs exhibit enhanced
chemotherapy efficacy toward T24 bladder cancer cells, owing to successful
magnetic guidance, pH-responsive release, and improved cellular uptake,
which give these NPs great potential as therapeutic agents for future
in vivo drug delivery systems.
In an effort to elucidate the mechanism of movement of nanovehicles on nonconducting surfaces, the synthesis and optical properties of five fluorescently tagged nanocars are reported. The nanocars were specifically designed for studies by single-molecule fluorescence spectroscopy and bear a tetramethylrhodamine isothiocyanate fluorescent tag for excitation at 532 nm. The molecules were designed such that the arrangement of their molecular axles and p-carborane wheels relative to the chassis would be conducive to the control of directionality in the motion of these nanovehicles.
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