Arkadij Sobolev

Use of pyridinium ionic liquids as catalysts for the synthesis of 3,5-bis(dodecyloxycarbonyl)-1,4-dihydropyridine derivative

AbstractThe synthesis of cationic amphiphilic 1,4-dihydropyridine derivative, potential gene delivery agent is achieved via an efficient multi-step sequence. The key step of this approach is a two-component Hantzsch type cyclisation of 3-oxo-2-[1-phenylmethylidene]-butyric acid dodecyl ester and 3-amino-but-2-enoic acid dodecyl ester utilising bis(2-hydroxyethyl)ether as a solvent and 1-butyl-4-methylpyridinium chloride as a catalyst. The 1,4-dihydropyridine derivative with long alkyl ester chains at positions 3 and 5 of the 1,4-DHP ring — 3,5-bis(dodecyloxycarbonyl)-2,6-dimethyl-4-phenyl-1,4-dihydropyridine was obtained in substantially higher yield with respect to classical Hantzsch synthesis. Bromination of this compound followed by nucleophilic substitution of bromine with pyridine gave the desired cationic amphiphilic 1,4-dihydropyridine.

Candida antarctica lipase-catalyzed hydrolysis of 4-substituted bis(ethoxycarbonylmethyl) 1,4-dihydropyridine-3,5-dicarboxylates as the key step in the synthesis of optically active dihydropyridines

Abstract Prochiral bis(ethoxycarbonylmethyl) substituted 4-aryl-1,4-dihydropyridine-3,5-dicarboxylates were hydrolyzed enantioselectively by Candida antarctica lipase B (Novozym 435). The enantiomeric excesses varied from 68 to 93%, depending on the substituent at position 4. In some cases, the e.e. could be significantly increased by changing the solvent system.

Enantioselective lipase-catalysed kinetic resolution of acyloxymethyl and ethoxycarbonylmethyl esters of 1,4-dihydroisonicotinic acid derivatives

Abstract The lipase-catalysed kinetic resolution of four derivatives of 4-[(acyloxy)methyl] and 4-ethoxycarbonylmethyl 3-methyl 5-propyl 2,6-dimethyl-1,4-dihydro-3,4,5-pyridinetricarboxylates has been investigated. Whereas the enantioselectivity of lipases towards the acyloxymethyl derivatives was rather low, the Candida antarctica lipase B (Novozym 435®, CAL-B)-catalysed hydrolysis of the ethoxycarbonylmethyl ester of 1,4-dihydroisonicotinic acid was enantioselective. In water-saturated diisopropyl ether at 45°C the enantioselectivity of CAL-B toward the ethoxycarbonylmethyl ester was rather moderate (E=13.8), but it was enhanced at rt and +4°C (E=21.5 and E=28.9, respectively). A high enantiomeric ratio (E=45.3) was reached at subzero temperatures, although at the expense of the reaction rate.

Chemoenzymatic synthesis of enantiopure 1,4-dihydropyridine derivatives

1,4-Dihydropyridines possess a broad range of biological activities, such as the ability to control the influx of calcium into cells, as well as neuroprotective, antineurodegenerative, cognition and memory enhancing, anti-inflammatory, antiviral and many other properties. Chirality plays an important role in the biological activity of 1,4-dihydropyridines. The chemoenzymatic synthesis of 1,4-dihydropyridine derivatives in enantiopure form as the key intermediates for the synthesis of enantiopure drugs and chiral analogues of symmetrical drugs has become an advantageous alternative to the other synthetic methods. Hydrolytic enzymes, as efficient chemo-, regio- and stereoselective biocatalysts have been successfully applied for the asymmetrisation or kinetic resolution of various 1,4-dihydropyridine derivatives. Several synthetic strategies to overcome the inactivity of hydrolytic enzymes towards 1,4-dihydropyridine carboxylic acids have been developed during the last decade, often based on the introduction of a spacer between an enzymatically labile group and the 1,4-DHP nucleus. Good to excellent enantioselectivities can be obtained by careful optimisation of the reaction temperature and the organic (co)solvent used in the enzymatic transformations.

An efficient chemoenzymatic approach to enantiomerically pure 4-[2-(difluoromethoxy)phenyl] substituted 1,4-dihydropyridine-3,5-dicarboxylates

Abstract An efficient chemoenzymatic synthesis of (−)-3-methyl 5-(2-propoxyethyl) (4 R )-4-[2-(difluoromethoxy)phenyl]-2,6-dimethyl-1,4-dihydro-3,5-pyridinedicarboxylate has been achieved. The key step is a highly stereoselective Candida rugosa lipase (CRL)-mediated asymmetrisation of the prochiral bis[(isobutyryloxy)methyl]-4-[2-(difluoromethoxy)phenyl]-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate.

Gene delivery agents possessing antiradical activity: self-assembling cationic amphiphilic 1,4-dihydropyridine derivatives

Seventeen 1,4-dihydropyridine (1,4-DHP) amphiphiles including differently substituted pyridinium, pyrazinium, N-methyl piperidinium or N-methyl morpholinium moieties as the cationic head-group of the molecule have been designed and synthesised. 1,4-DHP amphiphiles have been earlier proposed as a promising tool for plasmid DNA (pDNA) delivery in vitro. In this work the ability of the 1,4-DHP amphiphiles to self-assemble, to bind pDNA and to transfer it into the cells as well as the cytotoxicity of 1,4-DHP amphiphiles–pDNA complexes was studied. Furthermore, antiradical activity (ARA) of the 1,4-DHP derivatives was determined. We have revealed that all new 1,4-DHP amphiphiles possessed self-assembling properties and formed nanoparticles in an aqueous environment. The structure of the cationic head-group of 1,4-DHP amphiphiles influenced the size of nanoparticles. Additionally, we demonstrated for the first time that the electronic nature of the substituent of the pyridinium as the cationic head-group of the 1,4-DHP amphiphiles strongly affected the ability of these compounds to bind pDNA and transfer it into the cells. The amphiphiles with electron-donating properties possessing substituents at pyridinium moieties were able to bind pDNA and to deliver it more efficiently than amphiphiles containing electron-withdrawing properties possessing substituents at pyridinium moieties. Moreover, in this study we have established that the presence of the cationic part in the molecule was essential for the expression of ARA among tested 1,4-DHP amphiphiles. Cationic 1,4-DHP derivatives containing pyrazinium or N-methyl morpholinium substituents in the cationic head-group of the molecule displayed the highest ARA.

Studies of the physicochemical and structural properties of self-assembling cationic pyridine derivatives as gene delivery agents

New amphiphilic pyridine derivatives containing dodecyloxycarbonyl substituents at positions 3 and 5 and cationic moieties at positions 2 and 6 have been designed and synthesised. Compounds of this type can be considered as synthetic lipids. The corresponding 1,4-dihydropyridine (1,4-DHP) derivatives have earlier been proposed as a promising tool for plasmid DNA (pDNA) delivery in vitro. In this work studies of the self-assembling properties of amphiphilic pyridine derivatives leading to the formation of liposomes, determination of particle size, zeta-potential and critical micelle concentration (CMC) with dynamic light scattering (DLS) measurements are described. Furthermore, thermal analysis of pyridine derivatives was performed using thermogravimetry analysis (TGA) and differential thermal analysis (DTA) as well as the ability to deliver the pEGFP-C1 plasmid DNA (that encodes GFP reporter) into the Baby hamster kidney-derived (BHK-21) cell line was used for evaluation of gene delivery properties. We have revealed that the new pyridine derivatives possessed self-assembling properties which were proved by formation of nanoparticles with the average size from 115 to 743nm, the zeta-potentials in the range of 48-79mV and CMC values in the range of 2-67μM. DTA data showed that all processes were endothermic for all compounds. Additionally, we established that among the tested pyridines the representatives with N-methylpyrrolidinium or pyridinium moieties as cationic head-group at the positions 2 and 6 possessed higher pEGFP-C1 transfection activity into the BHK-21 cell line. Nevertheless, the obtained results indicated that correlation of the physicochemical, structural properties and gene delivery activities of the tested compounds were not completely elucidated yet. On the other hand, the synthesised pyridines as possible metabolites of promising delivery systems on the 1,4-DHP core possessed lower pDNA transfection activity than the corresponding 1,4-DHP amphiphiles.

Candida Rugosa Lipase-catalyzed Kinetic Resolution of 3-(Isobutyryloxy)methyl 4-[2-(Difluoromethoxy)phenyl]-2-methyl-5,5-dioxo-1,4-dihydrobenzothieno[3,2-b]pyridine-3-carboxylate

The lipase-catalyzed kinetic resolution of 3-(isobutyryloxy)methyl 4-[2-(difluoromethoxy)phenyl]-2-methyl-5,5-dioxo-1,4-dihydrobenzothieno[3,2-b]pyridine-3-carboxylate has been performed. The most enantioselective reaction (E = 28) was transesterification with n-butanol in water-saturated toluene at 45°C.

4-(10-methyl-10h-phenothiazin-3-yl)-1,4-dihydropyridines, 4,5 -dihydroindeno [1,2 -b]-and 5,5-dioxo-4,5-dihydrobenzo-thieno[3,2-b]pyridines

Different modifications of the Hantzsch synthesis using 10-methyl-10H-phenothiazine-3-carbaldehyde gave 4-(10-methyl-10H-phenothiazin-3-yl)-substituted 1,4-dihydropyridine-3,5-di-, 5-oxo-4,5-dihydro-1H-indeno[1,2-b]pyridine-, and 5,5-dioxo-4,5-dihydro-1H-5λ6-benzo[4,5]thieno[3,2-b]pyridine-3-carboxylic esters.

Direct Aminolysis of Ethoxycarbonylmethyl 1,4-Dihydropyridine-3-carboxylates

The ethoxycarbonylmethyl esters of 1,4-dihydropyridines were directly converted into carbamoylmethyl esters in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in good to excellent yields under mild conditions. The use of TBD is crucial for the successful aminolysis of ethoxycarbonylmethyl ester of 1,4-dihydropyridines with secondary amines as without it the reaction does not proceed at all. The aminolysis reaction proceeded regioselectively, as the alkyl ester conjugated with the 1,4-dihydropyridine cycle was not involved in the reaction. Screening of other N-containing bases, such as triethylamine (TEA), pyridine, 4-(N,N-dimethylamino)pyridine (DMAP), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), imidazole, tetramethyl guanidine (TMG) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) as catalysts revealed no activity in the studied reaction.