The
axially chiral tetra-ortho-substituted biaryl skeleton exists
in numerous biologically important natural products, pharmaceutical
molecules, chiral catalysts, and ligands. The efficient synthesis
of chiral tetra-ortho-substituted biaryl structures remains a challenging
but unsolved problem. Among various asymmetric synthetic protocols,
enantioselective Suzuki-Miyaura cross-coupling represents one of the
most straightforward and versatile approaches. Herein we describe
a powerful Suzuki-Miyaura coupling enabled by a P-chiral monophosphorus
ligand BaryPhos, providing a broad range of synthetically challenging
chiral tetra-ortho-substituted biaryls in excellent enantioselectivities
and yields. In addition to the enhanced reactivity for sterically
hindered cross-coupling, the rational design of BaryPhos also enabled
a new catalysis mode of asymmetric cross-coupling involving noncovalent
interactions between the ligand and two coupling partners to effect
efficient stereoinduction. This protocol is robust and practical,
allowing for a concise enantioselective synthesis of therapeutically
valuable male contraceptive and antitumor agent gossypol.
Garmultins A and B (1 and 2), two polycyclic polyprenylated acylphloroglucinols characterized by the coupling of two novel cages, 2,11-dioxatricyclo[4.4.1.0]undecane and tricyclo[4.3.1.0]decane, along with five biogenetically related analogues (3-7), were isolated from Garcinia multiflora. Their structures and absolute configurations were determined by extensive NMR analysis, X-ray crystallography, and electronic circular dichroism calculations. Three compounds were capable of inhibiting oncogene expression and inducing apoptosis in human erythroleukemia cells.
Objective: The aim of this study was to investigate the
cellular effects of melittin on the growth and apoptosis of
human hepatocellular carcinoma (HCC) cells and to provide
the molecular mechanism for potential application
of a recombinant adenovirus carrying the melittin gene
(Ad-rAFP-Mel) in the treatment of liver cancer. Methods:
Human HCC cells (BEL-7402) were infected with Ad-rAFPMel
at different times. In vitro cell growth was determined
by MTT assay. Cellular apoptosis was evaluated
quantitatively and qualitatively by phase-contrast microscopy,
transmission electron microscopy, DNA ladder
electrophoresis, TUNEL staining and flow cytometry. Results:
Ad-rAFP-Mel infection had an inhibitory effect on
the proliferation of BEL-7402 cells. The morphological
changes of apoptosis were confirmed by microscopy and
DNA electrophoresis. The ultrastructural characteristics
of apoptotic cells, such as chromatin condensation and
nuclear fragmentation, were also observed by electron
microscopy in the Ad-rAFP-Mel-infected cells. Ad-rAFPMel
infection markedly induced cellular apoptosis, and
Fas expression on Bel-7402 cells infected by Ad-rAFPMel
was up-regulated. Conclusion: The fact that melittin
can induce apoptosis of the HCC cell line BEL-7402 leads
us to consider adenovirus-mediated delivery of melittin
as a promising approach for the treatment of HCC. However,
the underlying mechanism needs to be further investigated.
Three indole alkaloid glycosides, strobilanthosides A-C (1-3), two known indole alkaloid glucosides (4 and 5), and five phenylethanoid glycosides (8-10) were isolated from the aerial parts of Strobilanthes cusia. The structures of the new compounds were elucidated by spectrometric analysis, and the absolute configurations of 1 and 2 were established by ECD spectrocsopy. N'-β-d-Glucopyranosylindirubin (5) showed weak antibacterial activity (MIC 62.5-125 μM) against Staphylococcus aureus.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.