An
efficient, diastereoselective synthesis of densely functionalized
pyrroloindolines is reported. The reaction proceeds via cycloaddition
of a vinylaziridine-derived Pd-stabilized 1,3-dipole to electron-deficient
3-nitroindoles. The reactions give the trans diastereoisomer
with high selectivity; however, when a 4-substituent is present on
the indole ring, a reversal of diastereoselectivity is observed.
A trans-diastereoselective Pd-catalyzed dearomative
[3 + 2] cycloaddition between vinylcyclopropane dicarboxylates and
3-nitroindoles has been developed. The reaction provides densely functionalized
cyclopenta[b]indolines with versatile vinyl and nitro-groups.
The addition of a halide additive was found to be critical for the
diastereoselectivity of the reaction, which is proposed to be a result
of a rapid π-σ-π interconversion between the intermediates
allowing for Curtin–Hammett control. A switch in diastereoselectivity
to afford products with the vinyl and nitro groups cis to each other is observed with a 4-substituted 3-nitroindole.
Targeting epigenetic mechanisms has shown promise against several cancers but has so far been unsuccessful against glioblastoma (
GBM
). Altered histone 3 lysine 4 methylation and increased lysine‐specific histone demethylase 1A (
LSD
1) expression in
GBM
tumours nonetheless suggest that epigenetic mechanisms are involved in
GBM
. We engineered a dual‐action prodrug, which is activated by the high hydrogen peroxide levels associated with
GBM
cells. This quinone methide phenylaminecyclopropane prodrug releases the
LSD
1 inhibitor 2‐phenylcyclopropylamine with the glutathione scavenger
para
‐quinone methide to trigger apoptosis in
GBM
cells. Quinone methide phenylaminocyclopropane impaired
GBM
cell behaviours in two‐dimensional and three‐dimensional assays, and triggered cell apoptosis in several primary and immortal
GBM
cell cultures. These results support our double‐hit hypothesis of potentially targeting
LSD
1 and quenching glutathione, in order to impair and kill
GBM
cells but not healthy astrocytes. Our data suggest this strategy is effective at selectively targeting
GBM
and potentially other types of cancers.
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The AMP-activated protein kinase (AMPK) αβγ heterotrimer is a primary cellular energy sensor and central regulator of energy homeostasis. Activating skeletal muscle AMPK with small molecule drugs improves glucose uptake and provides opportunity for new strategies to treat type 2 diabetes and insulin resistance, with recent genetic and pharmacological studies indicating the α2β2γ1 isoform combination as the heterotrimer complex primarily responsible. With the goal of developing α2β2-specific activators, here we perform structure/function analysis of the 2-hydroxybiphenyl group of SC4, an activator with tendency for α2-selectivity that is also capable of potently activating β2 complexes. Substitution of the LHS 2-hydroxyphenyl group with polar-substituted cyclohexene-based probes resulted in two AMPK agonists, MSG010 and MSG011, which did not display α2-selectivity when screened against a panel of AMPK complexes. By radiolabel kinase assay, MSG010 and MSG011 activated α2β2γ1 AMPK with one order of magnitude greater potency than the pan AMPK activator MK-8722. A crystal structure of MSG011 complexed to AMPK α2β1γ1 revealed a similar binding mode to SC4 and the potential importance of an interaction between the SC4 2-hydroxyl group and a2-Lys31 for directing α2-selectivity. MSG011 induced robust AMPK signalling in mouse primary hepatocytes and commonly used cell lines, and in most cases this occurred in the absence of changes in phosphorylation of the kinase activation loop residue α-Thr172, a classical marker of AMP-induced AMPK activity. These findings will guide future design of α2β2-selective AMPK activators, that we hypothesise may avoid off-target complications associated with indiscriminate activation of AMPK throughout the body.
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