A general carbonyl alkylative amination for tertiary amine synthesis.

The ubiquity of tertiary alkylamines in pharmaceutical and agrochemical agents, natural products and small-molecule biological probes1,2 has stimulated efforts towards their streamlined synthesis3-9. Arguably the most robust method for the synthesis of tertiary alkylamines is carbonyl reductive amination3, which comprises two elementary steps: the condensation of a secondary alkylamine with an aliphatic aldehyde to form an all-alkyl-iminium ion, which is subsequently reduced by a hydride reagent. Direct strategies have been sought for a 'higher order' variant of this reaction via the coupling of an alkyl fragment with an alkyl-iminium ion that is generated in situ10-14. However, despite extensive efforts, the successful realization of a 'carbonyl alkylative amination' has not yet been achieved. Here we present a practical and general synthesis of tertiary alkylamines through the addition of alkyl radicals to all-alkyl-iminium ions. The process is facilitated by visible light and a silane reducing agent, which trigger a distinct radical initiation step to establish a chain process. This operationally straightforward, metal-free and modular transformation forms tertiary amines, without structural constraint, via the coupling of aldehydes and secondary amines with alkyl halides. The structural and functional diversity of these readily available precursors provides a versatile and flexible strategy for the streamlined synthesis of complex tertiary amines.

Design, synthesis and biological evaluation of novel desloratadine derivatives with anti-inflammatory and H1 antagonize activities.

To improve the anti-inflammatory activity of desloratadine, we designed and synthesized a series of novel desloratadine derivatives. All compounds were evaluated for their anti-inflammatory and H1 antagonistic activities. Among them, compound 2c showed the strongest H1 antagonistic and anti-inflammatory activity. It also exhibited promising pharmacokinetic profiles and low toxicity. All these results suggest that compound 2c as a novel anti-allergic agent is worthy of further investigation.

Design, synthesis and bioevaluation of tricyclic fused ring system as dual binding site acetylcholinesterase inhibitors.

Due to recently discovered non-classical acetylcholinesterase (AChE) function, dual binding-site AChE inhibitors have acquired a paramount attention of drug designing researchers. The unique structural arrangements of AChE peripheral anionic site (PAS) and catalytic site (CAS) joined by a narrow gorge, prompted us to design the inhibitors that can interact with dual binding sites of AChE. Eighteen homo- and heterodimers of desloratadine and carbazole (already available tricyclic building blocks) were synthesized and tested for their inhibition potential against electric eel acetylcholinesterase (eeAChE) and equine serum butyrylcholinesterase (eqBChE). We identified a six-carbon tether heterodimer of desloratadine and indanedione based tricyclic dihydropyrimidine (4c) as potent and selective inhibitor of eeAChE with IC50 value of 0.09 ±â€¯0.003 µM and 1.04 ±â€¯0.08 µM (for eqBChE) with selectivity index of 11.1. Binding pose analysis of potent inhibitors suggest that tricyclic ring is well accommodated into the AChE active site through hydrophobic interactions with Trp84 and Trp279. The indanone ring of most active heterodimer 4b is stabilized into the bottom of the gorge and forms hydrogen bonding interactions with the important catalytic triad residue Ser200.

Synthesis of (18) F-Difluoromethylarenes from Aryl (Pseudo) Halides.

A general method for the synthesis of [(18) F]difluoromethylarenes from [(18) F]fluoride for radiopharmaceutical discovery is reported. The method is practical, operationally simple, tolerates a wide scope of functional groups, and enables the labeling of a variety of arenes and heteroarenes with radiochemical yields (RCYs, not decay-corrected) from 10 to 60 %. The (18) F-fluorination precursors are readily prepared from aryl chlorides, bromides, iodides, and triflates. Seven (18) F-difluoromethylarene drug analogues and radiopharmaceuticals including Claritin, fluoxetine (Prozac), and [(18) F]DAA1106 were synthesized to show the potential of the method for applications in PET radiopharmaceutical design.

Loratadine analogues as MAGL inhibitors.

Compound 12a (JZP-361) acted as a potent and reversible inhibitor of human recombinant MAGL (hMAGL, IC50=46 nM), and was found to have almost 150-fold higher selectivity over human recombinant fatty acid amide hydrolase (hFAAH, IC50=7.24 µM) and 35-fold higher selectivity over human α/ß-hydrolase-6 (hABHD6, IC50=1.79 µM). Additionally, compound 12a retained H1 antagonistic affinity (pA2=6.81) but did not show cannabinoid receptor activity, when tested at concentrations ⩽ 10 µM. Hence, compound 12a represents a novel dual-acting pharmacological tool possessing both MAGL-inhibitory and antihistaminergic activities.

Synthesis and biological evaluation of substituted desloratadines as potent arginine vasopressin V2 receptor antagonists.

Twenty-one non-peptide substituted desloratadine class compounds were synthesized as novel arginine vasopressin receptor antagonists from desloratadine via successive acylation, reduction and acylation reactions. Their structures were characterized by 1H-NMR and HRMS, their biological activity was evaluated by in vitro and in vivo studies. The in vitro binding assay and cAMP accumulation assay indicated that these compounds are potent selective V2 receptor antagonists. Among them compounds 1n, 1t and 1v exhibited both high affinity and promising selectivity for V2 receptors. The in vivo diuretic assay demonstrated that 1t presented remarkable diuretic activity. In conclusion, 1t is a potent novel AVP V2 receptor antagonist candidate.

Design, synthesis and biological activity evaluation of desloratadine analogues as H1 receptor antagonists.

A series of N-substituted desloratadine analogues were designed and synthesized. They were tested for H1 antihistamine activity by inhibiting histamine-induced contraction of isolated ileum muscles of guinea-pigs in vitro and inhibiting histamine-induced asthmatic reaction in guinea-pigs in vivo. All the evaluated compounds exhibited significant antihistamine activity compared with desloratadine. Five active compounds induced no sedative effects on mouse and four of them exhibited lower anticholinergic side effects than desloratadine. Among these analogues, compound 10, (1S,4S)-4-chlorocyclohexyl desloratadine displayed the highest activity and best safety profile. And it was believed to be a potential candidate as the 3rd generation antihistamine.

Design, synthesis and antihistamine evaluations of several N-hydroxyalkyl desloratadine analogues.

Several N-hydroxyalkyl desloratadines and N-methoxyl ethyl desloratadine were prepared and evaluated for H1 antihistamine activity. The effects on isolated ileum smooth muscle tension in guinea pigs in vitro and asthma-relieving effects on the histamine-induced asthmatic reaction in guinea-pigs in vivo were examined. Most of them exhibited satisfactory H1 antihistamine activity and were obviously more potent than loratadine. Among these, Compound 3, N-(3-hydroxy)propyl desloratadine was the most active one. And it was chosen as a candidate for evaluation of acute toxicity (LD(50)= 0.876(0.784-0.980) g/kg), significantly superior to that of desloratadine (LD(50)=0.353 g/kg). Meanwhile, the experimental results demonstrated that the oxygen atom in the side carbon chain is crucial for enhancing the antihistamine activities.

Synthesis and antihistamine evaluations of novel loratadine analogues.

A series of loratadine analogues containing hydroxyl group and chiral center were synthesized. The effect of the synthesized compounds on the histamine-induced contractions of guinea-pig ileum muscles was studied. In addition, the in vivo asthma-relieving effect of the analogues in the histamine induced asthmatic reaction in guinea-pigs was determined. Most of the compounds exhibited definite H(1) antihistamine activity. The S-enantiomers, compounds 2, 4 and 8, are more potent than the R-enantiomers, compounds 1, 3 and 7. Compound 6 was the most active one among the eight synthesized compounds.

Stereoselective synthesis of desloratadine derivatives as antagonist of histamine.

A series of desloratadine derivatives were stereoselectively synthesized and evaluated for H(1) antihistamine activity. For the evaluation of H(1) antihistamine activity, the in vitro histamine-induced contraction of the guinea-pig ileum assay (HC) was used. The synthesized desloratadine derivatives 7, 8 and 9 are structurally related to rupatadine and were generated by replacement of the 5-methyl-3-pyridine group of rupatadine with gamma-alkylidene butenolide. Their H(1) antihistamine activities have shown a high dependence on the exact nature of the substituent in the lactone ring. Optimum structures 7, 8a and 8g display potent activity inhibiting histamine-induced effects.

Hybrid approach for the design of highly affine and selective dopamine D(3) receptor ligands using privileged scaffolds of biogenic amine GPCR ligands.

A series of compounds containing privileged scaffolds of the known histamine H(1) receptor antagonists cetirizine, mianserin, ketotifen, loratadine, and bamipine were synthesized for further optimization as ligands for the related biogenic amine binding dopamine D(3) receptor. A pharmacological screening was carried out at dopamine D(2) and D(3) receptors. In the preliminary testing various ligands have shown moderate to high affinities for dopamine D(3)receptors, for example, N-(4-{4-[benzyl(phenyl)amino]piperidin-1-yl}butylnaphthalen-2-carboxamide (19a) (hD(3)K(i)=0.3 nM; hD(2)K(i)=703 nM), leading to a selectivity ratio of 2343.