Rearrangement of oximes and hydroxylamines with aluminum reductants

Design, synthesis and biological evaluation of brain penetrant benzazepine-based histone deacetylase 6 inhibitors for alleviating stroke-induced brain infarction

Histone deacetylase 6 (HDAC6) has become a promising therapeutic target for central nervous system diseases due to its more complex protein structure and biological functions. However, low brain penetration of reported HDAC6 inhibitors limits its clinical application in neurological disorders. Therefore, the benzazepine, a brain-penetrant rigid fragment, was utilized to design a series of selective HDAC6 inhibitors to improve brain bioavailability. Various synthetic strategies were applied to assemble the tetrahydro-benzazepine ring, and 22 compounds were synthesized. Among them, compound 5 showed low nanomolar potency and strong isozyme selectivity for the inhibition of HDAC6 (IC₅₀ = 1.8 nM, 141-fold selectivity over HDAC1) with efficient binding patterns like coordination with the zinc ion and π-π stacking effect. Western blot results showed it could efficiently transport into SH-SY5Y cells and selectively enhance the acetylation level of α-tubulin with a moderate effect on Histone H3. Notably, pharmacokinetic studies demonstrated that compound 5 (brain/plasma ratio of 2.30) had an excellent ability to penetrate the blood-brain barrier of C57 mice. In male rats with transient middle cerebral artery occlusion (MCAO), compound 5 significantly reduced the cerebral infarction from 21.22% to 11.47% and alleviated neurobehavioral deficits in post-ischemic treatment, which provided a strong rationale for pursuing HDAC6-based therapies for ischemic stroke.

Mild reductive rearrangement of oximes and oxime ethers to secondary amines with hydrosilanes catalyzed by B(C6F5)3

Oximes, its ether derivatives and the corresponding hydroxylamines rearrange to secondary amines when reacted with PhSiH₃ and B(C₆F₅)₃ as catalyst. Computations suggest a reduction–rearrangement to be slightly favored over a Beckmann-type sequence.

Oximes and Hydrazones in Bioconjugation: Mechanism and Catalysis

The formation of oximes and hydrazones is employed in numerous scientific fields as a simple and versatile conjugation strategy. This imine-forming reaction is applied in fields as diverse as polymer chemistry, biomaterials and hydrogels, dynamic combinatorial chemistry, organic synthesis, and chemical biology. Here we outline chemical developments in this field, with special focus on the past ∼10 years of developments. Recent strategies for installing reactive carbonyl groups and α-nucleophiles into biomolecules are described. The basic chemical properties of reactants and products in this reaction are then reviewed, with an eye to understanding the reaction's mechanism and how reactant structure controls rates and equilibria in the process. Recent work that has uncovered structural features and new mechanisms for speeding the reaction, sometimes by orders of magnitude, is discussed. We describe recent studies that have identified especially fast reacting aldehyde/ketone substrates and structural effects that lead to rapid-reacting α-nucleophiles as well. Among the most effective new strategies has been the development of substituents near the reactive aldehyde group that either transfer protons at the transition state or trap the initially formed tetrahedral intermediates. In addition, the recent development of efficient nucleophilic catalysts for the reaction is outlined, improving greatly upon aniline, the classical catalyst for imine formation. A number of uses of such second- and third-generation catalysts in bioconjugation and in cellular applications are highlighted. While formation of hydrazone and oxime has been traditionally regarded as being limited by slow rates, developments in the past 5 years have resulted in completely overturning this limitation; indeed, the reaction is now one of the fastest and most versatile reactions available for conjugations of biomolecules and biomaterials.

Cationic aluminum hydride complexes: reactions of carbene–alane adducts with trityl-borate

Reaction of (Idipp)AlH₃ with [Ph₃C][B(C₆F₅)₄] in toluene affords the dimeric aluminum dication [((Idipp)AlH(μ-H))₂][B(C₆F₅)₄]₂ with the corresponding reaction of (IBn)AlH₃ gives [(IBn)₂AlH][B(C₆F₅)₄]₂.