Catalytic Benzolactamization Through Isonitrile Insertion Enabled 1,4-Palladium Shift

<b>Isoindolinone is a class of versatile <i>N</i>-heterocycles embedded in many bioactive molecules and natural products. The invention of new methods to synthesize these heterocyclic compounds with easily accessible chemicals is always attractive. Herein, a conceptually novel approach to access this bicyclic system via isonitrile insertion enabled 1,4-pallaidum shift is described. Compared with conventional isonitrile participated C-H bond activation, both carbon and nitrogen atoms in isonitrile moiety are engaged in new bond formation. Notably, two different isoindolinones can be obtained selectively by switching the bases employed. Mechanistic studies including DFT calculations have shed lights on the reaction mechanism and explained the selectivity led to different products. Moreover, the power of current benzolactamization is further demonstrated by providing concise routes to key intermediates of indoprofen, indobufen, aristolactams, lennoxamine and falipamil.</b>

Catalytic Benzolactamization Through Isonitrile Insertion Enabled 1,4-Palladium Shift

<b>Isoindolinone is a class of versatile <i>N</i>-heterocycles embedded in many bioactive molecules and natural products. The invention of new methods to synthesize these heterocyclic compounds with easily accessible chemicals is always attractive. Herein, a conceptually novel approach to access this bicyclic system via isonitrile insertion enabled 1,4-pallaidum shift is described. Compared with conventional isonitrile participated C-H bond activation, both carbon and nitrogen atoms in isonitrile moiety are engaged in new bond formation. Notably, two different isoindolinones can be obtained selectively by switching the bases employed. Mechanistic studies including DFT calculations have shed lights on the reaction mechanism and explained the selectivity led to different products. Moreover, the power of current benzolactamization is further demonstrated by providing concise routes to key intermediates of indoprofen, indobufen, aristolactams, lennoxamine and falipamil.</b>

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

The 9-azabicyclo[3.3.1]nonane ring system is present in several insect- and plant-derived alkaloids. (−)-Adaline (1) and (+)-euphococcinine (2), found in secretions of Coccinelid beetles, and (+)-N-methyleuphococcinine (3), isolated from the Colorado blue spruce Picea pungens, are members of this alkaloid family. Their unique bicyclic system with a quaternary stereocenter, and the potent biological activity exerted by these homotropane alkaloids, make them attractive synthetic targets. This work aims briefly to review the chemical ecology of Adalia bipunctata and the recent methodologies to obtain adaline (1), euphococcinine (2), and N-methyleuphococcinine (3).

Synthesis and Antiplasmodial Activity of Novel Bioinspired Imidazolidinedione Derivatives

Malaria is an enormous threat to public health, due to the emergence of Plasmodium falciparum resistance to widely-used antimalarials, such as chloroquine (CQ). Current antimalarial drugs are aromatic heterocyclic derivatives, most often containing a basic component with an added alkyl chain in their chemical structure. While these drugs are effective, they have many side effects. This paper presents the synthesis and preliminary physicochemical characterisation of novel bioinspired imidazolidinedione derivatives, where the imidazolidinedione core was linked via the alkylene chain and the basic piperazine component to the bicyclic system. These compounds were tested against the asexual stages of two strains of P. falciparum—the chloroquine-sensitive (D10) and chloroquine-resistant (W2) strains. In parallel, in vitro cytotoxicity was investigated on a human keratinocyte cell line, as well as their hemolytic activity. The results demonstrated that the antiplasmodial effects were stronger against the W2 strain (IC50 between 2424.15–5648.07 ng/mL (4.98–11.95 µM)), compared to the D10 strain (6202.00–9659.70 ng/mL (12.75–19.85 µM)). These molecules were also non-hemolytic to human erythrocytes at a concentration active towards the parasite, but with low toxicity to mammalian cell line. The synthetized derivatives, possessing enhanced antimalarial activity against the CQ-resistant strain of P. falciparum, appear to be interesting antimalarial drug candidates.

Dibenzoate esters of cis-tetralin-2,3-diol as analogs of (–)-epigallocatechin gallate: synthesis and crystal structure of anticancer drug candidates

(−)-Epigallocatechin gallate (EGCG), the main component of green tea extract, displays multiple biological activities. However, it cannot be used as a drug due to its low cellular absorption, instability and metabolic degradation. Therefore, there is a need to provide analogs that can overcome the limitations of EGCG. In this work, six synthetic analogs of EGCG sharing a common tetralindiol dibenzoate core were synthesized and fully characterized by 1H NMR, 13C NMR, HRMS and IR spectroscopies, and X-ray crystallography. These are (2R,3S)-1,2,3,4-tetrahydronaphthalene-2,3-diyl bis[3,4,5-tris(benzyloxy)benzoate], C66H56O10, and the analogous esters bis(3,4,5-trimethoxybenzoate), C30H32O10, bis(3,4,5-trifluorobenzoate), C24H14F6O4, bis[4-(benzyloxy)benzoate], C38H32O6, bis(4-methoxybenzoate), C26H24O6, and bis(2,4,6-trifluorobenzoate), C24H14F6O4. Structural analysis revealed that the molecular shapes of these dibenzoate esters of tetralindiol are significantly different from that of previously reported dimandelate esters or monobenzoate esters, as the acid moieties extend far from the bicyclic system without folding back over the tetralin fragment. Compounds with small fluorine substituents take a V-shape, whereas larger methoxy and benzyloxy groups determine the formation of an L-shape or a cavity. Intermolecular interactions are dominated by π–π stacking and C—H...π interactions involving the arene rings in the benzoate fragment and the arene ring in the tetrahydronaphthalene moiety. All six crystal structures are determined in centrosymmetric space groups (either P-1, P21/n, C2/c or I2/a).

Selectivity Control in Terpene Rearrangements: A Biomimetic Synthesis of the Halimanic Bicyclic Core

The bicyclic core of the halimanic framework is synthesized in optically active form by an acid-induced rearrangement of a homo­drimanic epoxide. The substrate can follow two different pathways under acidic treatment. Using fluorosulfonic acid as a promoter at low temperature favors ring contraction to a perhydrindanic structure. In contrast, milder acids at higher temperatures bring about predominantly an angular methyl migration and formation of the halimanic bicyclic system. In particular, an acidic pillared clay selectively promoted this transformation.

SYNTHESIS OF NEW DERIVATIVES OF 3-AZABICYCLO[3.3.1]NONANES BASIS ON N-(2-HYDROXY-3,5-DINITROPHENYL)ACETAMIDE σ-ADDUCT

A number of new derivatives of N-(3-R-1,5-dinitro-8-oxo-3-azabicyclo[3.3.1]non-6-en-7-yl)acetamides have been synthesized by Mannich condensation of hydride σ-adduct of the N-(2-hydroxy-3,5-dinitrophenyl)acetamide with formaldehyde and primary amines. The synthesis was carried out with two stages. In the first stage, under the action of sodium tetrahydride borate on a solution of N-(2-hydroxy-3,5-dinitrophenyl)acetamide, the C = C bonds of the aromatic ring were reduced to form a 3-charge hydride adduct. The resulting diaduct was isolated from the solution and, while cooling with ice, was introduced into Mannich-condensation with formaldehyde and a solution of the primary amine or amino acid. When the reaction mixture was acidified with dilute orthophosphoric acid to pH 4–5, precipitates of the target products precipitated. After recrystallization from ethanol, the yield of the target products, depending on the substituent at the nitrogen atom, ranged from 55 to 90%. This method is distinguished by relative simplicity, availability of reagents and allows under mild conditions to transfer from the aromatic system activated by nitro groups to 3-azabicyclo[3.3.1]nonane derivatives, containing promising from the point of view of further functionalization nitro, carbonyl and amino groups. The structure of the compounds obtained was proved by IR, 1H-, 13C-, two-dimensional correlation NMR spectroscopy, as well as elemental analysis data. In the IR spectra of the obtained substances, the characteristic absorption bands of amide I (1629-1633 cm-1) and amide II (1560-1570 cm-1), as well as antisymmetric (1549-1556 cm-1) and symmetric (1370-1377 cm-1) oscillations of nitro groups were observed. In the NMR spectra in the weakest field, the broadened signal of the proton NH is observed (δ 9.51-9.57 ppm), followed by the singlet signal of the proton at the double bond (δ 8.15-8.16 ppm). The protons of the methylene groups of the bicyclic system are diastereotopic. Therefore, their signals are mutually split into broadened doublets located in the region of 2.66–3.46 ppm.

Synthesis, Characterization and Pharmacological evaluation of some newer Benzothiazole derivatives

The objective of the present work is to develop safer new chemical entities that show good anticonvulsant effects and antimicrobial actions. The current work describes the synthesis of Benzothiazole derivatives with encouraging anticonvulsant activity against MES and scPTZ tests with interesting pattern of antimicrobial effects. The synthesized Benzothiazole derivatives could be considered as lead molecule for the development of therapeutic agents. Many polycyclic and fused ring systems containing the thiazolenucleus(I) are well known. The most important is bicyclic system wherein the second ring benzene is fused to the 4,5 position of thiazole ring i.e. Benzothiazole.(II)