Fei Mao

Palladium‐Catalyzed Cross‐Dehydrogenative Functionalization of C(sp2)H Bonds

The catalytic cross-dehydrogenative coupling (CDC) reaction has received intense attention in recent years. The attractive feature of this coupling process is the formation of a C-C bond from two C-H moieties under oxidative conditions. In this Focus Review, recent advances in the palladium-catalyzed CDC reactions of C(sp(2) )-H bond are summarized, with a focus on the period from 2011 to early 2013.

Palladium-Catalyzed Oxidative C–H Bond Coupling of Steered Acetanilides and Aldehydes: A Facile Access to ortho-Acylacetanilides

A palladium-catalyzed oxidative C-H bond functionalization/ortho-acylation of acetanilides using easily accessible aldehyde as the acyl source is described. In the presence of a Pd(TFA)(2) catalyst and tert-butylhydroperoxide at 90 °C in general, an array of ortho-acylacetanilides can be afforded in good yields.

Intramolecular Direct C–H Bond Arylation from Aryl Chlorides: A Transition-Metal-Free Approach for Facile Access of Phenanthridines

A C-H arylation with aryl chloride is made viable through a transition-metal-free approach. In the presence of a simple diol associating with KOt-Bu, various phenanthridine derivatives can be conveniently accessed. In particular, only 10 mol % of simple and inexpensive ethylene glycol is required for this protocol. These results represent the first general examples of aryl chloride/C-H coupling under transition-metal-free conditions.

Multitarget-Directed Benzylideneindanone Derivatives: Anti-β-Amyloid (Aβ) Aggregation, Antioxidant, Metal Chelation, and Monoamine Oxidase B (MAO-B) Inhibition Properties against Alzheimer’s Disease

A novel series of benzylideneindanone derivatives were designed, synthesized, and evaluated as multitarget-directed ligands against Alzheimers disease. The in vitro studies showed that most of the molecules exhibited a significant ability to inhibit self-induced β-amyloid (Aβ(1-42)) aggregation (10.5-80.1%, 20 μM) and MAO-B activity (IC(50) of 7.5-40.5 μM), to act as potential antioxidants (ORAC-FL value of 2.75-9.37), and to function as metal chelators. In particular, compound 41 had the greatest ability to inhibit Aβ(1-42) aggregation (80.1%), and MAO-B (IC(50) = 7.5 μM) was also an excellent antioxidant and metal chelator. Moreover, it is capable of inhibiting Cu(II)-induced Aβ(1-42) aggregation and disassembling the well-structured Aβ fibrils. These results indicated that compound 41 is an excellent multifunctional agent for the treatment of AD.

Design, synthesis, and evaluation of indanone derivatives as acetylcholinesterase inhibitors and metal-chelating agents.

A series of novel indanone derivatives was designed, synthesised and evaluated as potential agents for Alzheimers disease. Among them, compound 6a, with a piperidine group linked to indone by a two-carbon spacer, exhibited the most potent inhibitor activity, with an IC(50) of 0.0018 μM for AChE; the inhibitory activity of this compound was 14-fold more potent than that of donepezil. Furthermore, these compounds also exhibited good metal-chelating ability.

Design, Synthesis, and Evaluation of Multitarget-Directed Selenium-Containing Clioquinol Derivatives for the Treatment of Alzheimer’s Disease

A series of selenium-containing clioquinol derivatives were designed, synthesized, and evaluated as multifunctional anti-Alzheimers disease (AD) agents. In vitro examination showed that several target compounds exhibited activities such as inhibition of metal-induced Aβ aggregation, antioxidative properties, hydrogen peroxide scavenging, and the prevention of copper redox cycling. A parallel artificial membrane permeation assay indicated that selenium-containing clioquinol derivatives possessed significant blood-brain barrier (BBB) permeability. Compound 8a, with a propynylselanyl group linked to the oxine, demonstrated higher hydrogen peroxide scavenging and intracellular antioxidant activity than clioquinol. Furthermore, 8a exhibited significant inhibition of Cu(II)-induced Aβ1-42 aggregation and was capable of disassembling the preformed Cu(II)-induced Aβ aggregates. Therefore, 8a is an excellent multifunctional promising compound for development of novel drugs for AD.

O-Hydroxyl- or o-amino benzylamine-tacrine hybrids: Multifunctional biometals chelators, antioxidants, and inhibitors of cholinesterase activity and amyloid-β aggregation

In an effort to identify novel multifunctional drug candidates for the treatment of Alzheimers disease (AD), a series of hybrid molecules were synthesised by reacting N-(aminoalkyl)tacrine with salicylic aldehyde or derivatives of 2-aminobenzaldehyde. These compounds were then evaluated as multifunctional anti-Alzheimers disease agents. All of the hybrids are potential biometal chelators, and in addition, most of them were better antioxidants and inhibitors of cholinesterases and amyloid-β (Aβ) aggregation than the lead compound tacrine. Compound 7c has the potential to be a candidate for AD therapy: it is a much better inhibitor of acetylcholinesterase (AChE) than tacrine (IC(50): 0.55 nM vs 109 nM), has good biometal chelation ability, is able to inhibit Aβ aggregation and has moderate antioxidant activity (1.22 Trolox equivalents).

Design, synthesis, and biological evaluation of benzoselenazole-stilbene hybrids as multi-target-directed anti-cancer agents

To identify novel multi-target-directed drug candidates for the treatment of cancer, a series of benzoselenazole-stilbene hybrids were synthesised by combining the pharmacophores of resveratrol and ebselen. The biological assay indicated that all of the hybrids exhibited antiproliferative activities against four human cancer cell lines and demonstrated good TrxR inhibitory activities. The mechanism of cell apoptosis was investigated in G2/M cell cycle arrest induced by compound 6e and the apoptosis of the human liver carcinoma Bel-7402 cell line. The significant increase in intracellular ROS confirmed that compound 6e was capable of causing oxidative stress-induced apoptosis in cancer cells. Our results support the potential of compound 6e as a candidate for further studies examining the development of novel drugs for cancer treatment.

Novel tacrine–ebselen hybrids with improved cholinesterase inhibitory, hydrogen peroxide and peroxynitrite scavenging activity

A series of tacrine-ebselen hybrids were synthesised and evaluated as possible multifunctional anti-Alzheimers disease (AD) agents. Compound 6i, which is tacrine linked with 5,6-dimethoxybenzo[d][1,2]selenazol-3(2H)-one by a six-carbon spacer, was the most potent acetylcholinesterase (AChE) and butylcholinesterase (BuChE) inhibitor, with IC50 values of 2.55 and 2.80 nM, respectively. Furthermore, this compound demonstrated similar hydrogen peroxide and peroxynitrite scavenging activity as ebselen by horseradish peroxidase assay and peroxynitrite scavenging activity assay, indicating that this hybrid is a good multifunctional drug candidate for the treatment of AD.

Hybrids consisting of the pharmacophores of salmeterol and roflumilast or phthalazinone: Dual β2-adrenoceptor agonists-PDE4 inhibitors for the treatment of COPD

A novel class of dual pharmacology bronchodilators targeting both β(2)-adrenoceptor and PDE4 was designed and synthesised by combining the pharmacophores of salmeterol and roflumilast or phthalazinone. All the compounds exhibited better β(2)-adrenoceptor agonist activities (pEC(50)=8.47-9.20) than the reference compound salmeterol (pEC(50)=8.3) and good inhibitory activity on PDE4B2 (IC(50)=0.235-1.093 μM).