Synthesis and structure of a new stable radical,di-(4-dimethylneopentylmethylphenyl)nitroxide

Russian Chemical Bulletin -     

Synthesis of new di- and triamine diosgenin dimers

In this study, a high yield synthesis of symmetrical steroidal polyamine dimers was achieved by the dimerization of (25R)-3β-acetoxyfurost-5-en-26-al via several di- and triamine linkers under mild conditions. To ensure the dimerization via E-E ring, the hydroxyl group in diosgenin was protected by an acetyl group. The important step is opening the spiroketal moiety using NaCNBH₃/AcOH to furnish the primary alcohol at C-26, followed by oxidation using PCC/CH₂Cl₂ to synthesize the desired aldehyde. Finally, reductive amination with diaminopropane, diaminobutane, diaminohexane, and spermidine using Na(OAc)₃BH as reducing agent, afforded the required four dimers.     

Bismethylene triphosphate nucleotides of uridine 4-phosphate analogues: a new class of anionic pyrimidine nucleotide analogues

Cytidine-5'-triphosphate synthase (CTPS) catalyzes the formation of cytidine triphosphate (CTP) from glutamine, uridine 5'-triphosphate (UTP), and adenosine 5'-triphosphate (ATP). This reaction proceeds via formation of the high-energy intermediate UTP-4-phosphate (UTP-4-P). Stable analogues of UTP-4-P may be potent inhibitors of CTPS and useful as lead structures for the development of anticancer and antiviral agents. Several bismethylene triphosphate (BMT) nucleotides of uridine 4-phosphate (U-4-P) analogues have been prepared. A key step was the selective methanolysis, with the aid of a tin catalyst, of the 5' ester moiety of 2',3',5'-tri-O-acetyl or tri-O-benzoyl U-4-P analogues. We believe this represents the first general approach to the selective cleavage of 5' benzoyl esters in benzoylated nucleosides. Mitsunobu coupling of these 5'-deprotected U-4-P analogues to an unsymmetrical, protected BMT bearing a free phosphonic acid moiety at one of the terminal positions gave fully protected BMT-U-4-P analogues. Global deprotection of these species was achieved using TMSBr followed by treatment with NH4OH-MeOH or NH4OH-pyridine. The resulting BMT nucleotides represent a new class of anionic pyrimidine nucleotide analogues.     

Characterization of TrdL as a 10-hydroxy dehydrogenase and generation of new analogues from a tirandamycin biosynthetic pathway

TrdL, encoding a flavin-dependent oxidoreductase in the tirandamycin gene cluster, was inactivated to afford a ΔtrdL mutant, the fermentation of which yielded a new intermediate, tirandamycin E (5), and an additional early intermediate, tirandamycin F (6), if XAD-16 resin was introduced. TrdL was overexpressed in E. coli, and the protein was shown to efficiently catalyze the transformations from 5 to tirandamycin A (1) and from 6 to tirandamycin D (4), demonstrating its function as a 10-hydroxy dehydrogenase.     

Synthesis of new lavendamycin analogues

Friedländer reaction between methyl acetoacetate and 2,4-diaminobenzaldehyde provided quinoline 11. Subsequent tosylation, reduction, silylation, and then oxidation led to aldehyde 15. The latter was subjected to a Pictet-Spengler reaction with tryptophan methyl ester that yielded product 16, and then desilylation gave the lavendamycin analogue 17. This compound was oxidized by Dess-Martin periodinane, and the cyclized derivative 18 was obtained via a hemiaminal intermediate. The same sequence from 2,4-diamino-5-methoxybenzaldehyde or from (2,4-diaminophenyl)propan-3-one led to compounds 30 and 31, or 40 and 41, respectively.     

Synthesis and properties of a new family of cyclodextrin analogues

The chemical synthesis of a series of cyclic oligosaccharides built up from (14)-linked alternatingD– andl-pyranosidic units is described for the first time. Key intermediates employed were disaccharides representing minimal repeating units. These disaccharides (monomers) have been prepared in specifically modified forms so that they bear both glycosyl donor (cyanoethylidene group) and glycosyl acceptor (trityloxy group) functions. Polycondensation-cyclisation of these disaccharide monomers, catalysed by TrC1O₄ under normal conditions of dilution, has led to series of homologous cyclic oligosaccharides with an even number of sugar residues (6, 8, 10, 12,etc.) in each case. Cyclic hexa- and octa-saccharides, based onl-rhamnose andD-mannose as the alternating monosaccharides units, have been deprotected to produce analogues of - and -cyclodextrins (CDs) and the X-ray crystal structure of the cyclic octasaccharide has been determined.     

Synthesis of new ribosylated Asn building blocks as useful tools for glycopeptide and glycoprotein synthesis

We performed the first synthesis of new Asn derivatives bearing α- or β-ribose as pure anomers, linked by an N-glycosidic bond, on the side chain of the Asn residue orthogonally protected for Fmoc/^tBu SPPS, by an efficient five-step strategy with a global yield of 73% starting from d-ribose. These building blocks are obtained in a large scale and can be useful tools for glycopeptide and glycoproteins synthesis.     

Synthesis of new analogues of diphenylpyraline

1-Unsubstituted 4-dimethylamino-5,6-dihydropyridine-2(1H)-thiones were converted to isomeric piperidin-4-ols which were separated and N-methylated to 2-substituted 1-methylpiperidin-4-ols. Their 1-phenyl analogues were prepared from 4-dimethylamino-5,6-dihydro-1-phenylpyridine-2(1H)-thiones. After their conversion to dihydro-1-phenylpyridin-4(1H)-ones the hydrogenation gave isomeric 1-phenylpiperidin-4-ols which were separated. O-Alkylation of the 1-substituted piperidin-4-ols by various methods yielded 2-substituted analogues of diphenylpyraline. Their antimycobacterial activity was examined. The configurations and conformations of the piperidine derivatives were investigated by NMR spectroscopy.     

Synthesis of new nucleoside analogues comprising a methylenecyclobutane unit

Synthesis of eight nucleoside analogues 3-10 with a methylene cyclobutane unit is described. Wittig or Peterson reactions with protected 2-hydroxycyclobutanones 12 and 13 gave E- and Z-derivatives, respectively. After functional modifications the heterocyclic moieties were introduced via a Mitsunobu reaction either on the lateral chain or on the cycle. When adenine was used in this reaction only the N-9 substitution products were obtained. Removal of the protecting groups provided the target products.     

Synthesis of new di-(3-indolyl)arenes

1,4-Di-(3-indolyl)benzene 6 and 2,8-di-(3-indolyl)dibenzofuran 12 were synthesized from 1,4-diacetylbenzene and 2,8-diacetyldibenzofuran, respectively, via indole synthetic strategies. Investigation into the acid-catalysed formation of macrocyclic systems from these di-(3-indolyl)arenes led to the development of the 18-membered macrocycle 14 from the diindolylbenzene 6, which was capable of undergoing complexation with nickel(II) ions.     

Synthesis of new series of iboga analogues

Synthesis of new iboga-analogues, replacing the indole ring with a benzofuran moiety has been described. Starting materials are the suitably substituted benzofuran derivatives and have been synthesized by Pd-catalyzed reactions. The conversion of endo-6-methylcarboxylate substituted dehydroisoquinuclidine to exo-isomer, a key component of iboga-alkaloids has been achieved in the presence of NaOMe in methanol under reflux conditions.     

Synthesis,modeling, and biological studies of new thiazole-pyrazole analogues as anticancer agents

A series of various substituted thiazole-pyrazole hybrids 5, 7, 8, and 9 were synthesized, and their chemical structures were confirmed by spectral data (infrared, ¹H & ¹³C NMR and Mass). The frontier molecular orbital structural and energetic properties of the targeting thiazole-pyrazole hybrids were explored using the DFT/B3LYP methodology. The data indicated that they had a low energy gap (ΔE_H-L), 1.51–2.42 eV, and may be sorted as 6 < 9 < 7 < 8 < 4 < 3 < 5. The synthesized thiazole-pyrazole hybrids were explored for their activities towards HepG2, MCF-7, and HCT-116 in contrast to doxorubicin. The newly synthesized thiazole-pyrazole analogues demonstrated an acceptable efficiency towards the HepG2 cancer cell line in accordance with this order: 8 > 9 > 7 > 6. Meanwhile, most of the synthesized analogues displayed a significant reduction for the activity of the CAIX inhibitor, with IC₅₀ = 0.071 ± 0.015 to 0.902 ± 0.043 µM. Likewise, they revealed an IC₅₀ = 0.119 ± 0.043 to 0.906 ± 0.04 µM for CAXII inhibitor. Moreover, the newly synthesized thiazole-pyrazole analogues were exposed to the theoretical molecular docking study with PDB:1RHJ as the crystal structure of caspase-3 to examine their antiapoptotic effect as well as their certain properties on the caspase-3 enzyme.     

Synthesis of new nitrogen analogues of salacinol and deoxynojirimycin and their evaluation as glycosidase inhibitors

The synthesis of two enantiomerically pure iminosugars, analogues of 1-L-deoxynojirimycin (l-DNJ) and 1-D-deoxymannojirimycin (DMJ), was achieved using cyclic sulfate substituted isoxazoline derivatives. The piperidine ring was formed via the reduction of an isoxazoline into an amine which underwent a spontaneous intramolecular cyclization by reaction with the cyclic sulfate moiety. The nucleophilic attack of these two trisubstituted piperidines and morpholine on L- and D-erythritol-1,3-cyclic sulfates gave six new nitrogen analogues of salacinol. The inhibitory properties of the synthesized salacinol analogues were evaluated on several commercial glycosidases.     

Synthesis of di- and tetrahydropyrroles

A method for the synthesis of 2,3,3-trimethyl-2-hydroxy-5-pyrrolidone has been developed. 3,3-Dimethyl-2-methylene-5-pyrrolidone is initially formed during its thermolysis and then readily dimerizes. 2,3,3-Trimethyl-2-cyano-5-pyrrolidone was synthesized by the reaction of 2,3,3-trimethyl-2-hydroxy-5-pyrrolidone with potassium cyanide.See [1] for communication VII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1190–1193, September, 1971.     

Synthesis and characterization of new thienylpyrrolyl-benzothiazoles as efficient and thermally stable nonlinear optical chromophores

The synthesis and full characterization of new chromophores with second-order nonlinearities containing thienylpyrrolyl and benzothiazolyl moieties are reported. The solvatochromic behavior of the compounds was investigated. The hyperpolarizabilities β of derivatives 4-6 were measured using hyper-Rayleigh scattering and thermogravimetric analysis (TGA) was used to evaluate their thermal stability. The experimental results indicate that strong nonlinearity is balanced by good thermal stability especially for chromophores 6b and 6c, making them good candidates for NLO applications.     

Synthesis,crystal structure and charge transport characteristics of stable peri-tetracene analogues

peri-Acenes have shown great potential for use as functional materials because of their open-shell singlet biradical character. However, only a limited number of peri-acene derivatives larger than peri-tetracene have been synthesized to date, presumably owing to the low stability of the target compounds in addition to the complicated synthesis scheme. Here, a very simple synthesis route for the tetrabenzo[a,f,j,o]perylene (TBP) structure enables the development of highly stable peri-tetracene analogues. Despite a high degree of singlet biradical character, the compounds with four substituents at the zigzag edge show a remarkable stability in solution under ambient conditions, which is better than that of acene derivatives with a closed-shell electronic configuration. The crystal structures of the TBP derivatives were obtained for the first time; these are valuable to understand the relationship between the structure and biradical character of peri-acenes. The application of peri-acenes in electronic devices should also be investigated. Therefore, the semiconducting properties of the TBP derivative were investigated by fabricating the field-effect transistors.

Highly stable peri-tetracene analogues with a high degree of singlet biradical character were synthesized in a very simple route, and their crystal structures and semiconducting properties were investigated.