Sirtuins are involved in epigenetic regulation, the pathogenesis of cancer, and several metabolic and neurodegenerative diseases. Despite being a promising drug target, only one small molecule passed class II clinical trials to date. Deriving a better mechanistic understanding is hence crucial to find new modulators. We previously reported on a series of dithienyl maleimides as photochromic tool compounds. However, their photochromic behavior was limited. To improve the interconversion and stability of both photoisomers, we replaced the dithienyl maleimide with a fulgimide as a photochromic core to result in biologically active compounds reversibly addressable with purple and orange light. We characterize the obtained compounds regarding their spectroscopic properties, their photostability, and binding characteristics toward sirtuins resulting in a fully remote-controllable Sirtuin modulator using visible light as the external stimulant.
Metal and catalyst‐free carbohydroxylations and carboetherifications at room temperature have been achieved by a combination of beneficial factors including high aryl diazonium concentration and visible light irradiation. The acceleration of the reaction by visible light irradiation is particularly remarkable against the background that neither the aryldiazonium salt nor the alkene show absorptions in the respective range of wavelength. These observations point to weak charge transfer interactions between diazonium salt and alkene, which are nevertheless able to considerably influence the reaction course. As highly promising perspective, many more aryldiazonium‐based radical arylations might benefit from simple light irradiation without requiring a photocatalyst or particular additive.
Aryl radicals generated
in the aqueous phase of biphasic mixtures
haveregardless of a comparably low polarity a strong
preference to react with aromatic substrates in the aqueous phase
and not to undergo phase-transfer into a lipophilic phase, independent
from the presence of a surfactant. These results represent an important
prerequisite toward future studies in biological systems, which typically
consist of various compartments of either hydrophilic or lipophilic
character.
The cleavage of representative lignin systems has been achieved in a metal‐free two‐step sequence first employing nitrogen monoxide for oxidation followed by hydrazine for reductive C−O bond scission. In combining nitrogen monoxide and lignin, the newly developed valorization strategy shows the particular feature of starting from two waste materials, and it further exploits the attractive conditions of a Wolff‐Kishner reduction for C−O bond cleavage for the first time.
From the variety
of methods known for the depolymerization of organosolv
lignin, a broad range of diversely substituted aromatic compounds
are available today. In the present work, a novel two-step reaction
sequence is reported, which is focused on the formation of phenols.
While the first step of the depolymerization strategy comprises the
2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-catalyzed oxidation
of organosolv lignin with nitrogen monoxide so that two waste materials
are combined, cleavage to the phenolic target compounds is achieved
in the second step employing hydrazine and potassium hydroxide under
Wolff–Kishner-type conditions. Besides the fact that the novel
strategy proceeds via an untypical form of oxidized organosolv lignin,
the two-step sequence is further able to provide phenols as cleavage
products, which bear no substituent at the 4-position.
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