Synthesis of a new conformationally constrained glycoamino acid building block

The synthesis of a suitably protected β-d-glucopyranosyl-(S)-α-methylserine derivative—a new conformationally constrained glycosylated quaternary amino acid analogue of β-d-glucopyranosyl-l-serine—is described. This compound can be used as an attractive building block for the synthesis of new, constrained glycopeptides.     

Synthesis and physiological activity of trialkyl phosphorothioates and trialkyl phosphorodithioates containing fragments of N-acylated amino acids

A series of S-[N-acyl-N-(alkoxycarbonylalkyl)aminomethyl] O,O-dialkyl phosphorothioates and -dithioates were prepared by the reactions of the corresponding alkali salts of dialkyl phosphorothioates or dialkyl phosphorodithioates with esters of N-acyl-N-(chloromethyl)glycine or N-acyl-N-(chloromethyl)--alanine and by the reactions of dialkylphosphorothioic or dialkylphosphorodithioic acids with N-acylated amino acids or their esters and paraformaldehyde in the presence of gaseous HCl. Some of the resulting compounds proved to be active permethrine synergists.     

Synthesis and characterization of 1,3,4-oxadiazole derivatives containing alkoxy chains with different lengths

The synthesis, optical properties, electrochemical properties, electronic structures and applications in electroluminescent device of three series of 1,3,4-oxadiazole derivatives, 1,4-bis[(4-methylphenyl)-1,3,4-oxadiazolyl]phenylene (OXD₁), 5,5′-di-(4-methyl)-2,2′-p-(2,5-bisalkoxyphenylene)-bis-1,3,4-oxadiazole (OXD_2–n) and 1,4-bis[(4-alkoxyphenyl)-1,3,4-oxadiazolyl]phenylene (OXD_3–n) are reported. The molecular structures of the oxadiazole compounds were confirmed by FT-IR, ¹H NMR spectroscopy and elemental analysis. The optical and electrochemical properties of the compounds were investigated by UV–vis absorption and photoluminescence spectroscopy as well as cyclic voltammetry. The results show that introduction of two alkoxy groups whose electron-donating ability is stronger than that of methyl groups increases the electron density of the conjugated segment of OXD_2–n (with side-on alkoxy substituents) and OXD_3–n (with end-on alkoxy substituents), and thus leads to the absorption maximum bathochromic-shift compared to that of OXD₁. The HOMO and LUMO energy levels of the compounds studied are in the range of −2.78 to −2.89 and −5.75 to −6.20 eV. Calculations on the representative compounds by the Dmol³ package of MS Modeling 3.0 revealed that the increase of energy levels in both OXD_2–n and OXD_3–n was due to the change of the frontier molecular orbital distribution in the central benzene ring. The light-emitting devices have been fabricated using blends of MEH-PPV and these compounds as emissive layers, among which, maximum brightness up to 11810 cd m⁻² (8.5 V) has been observed, which is 40 times brighter than that with MEH-PPV. The result of the devices suggested that oxadiazole derivatives studied function well as electron-transporting materials and can be used in LEDs, and thus to enhance the efficiency of LEDs.     

Synthesis, characterization and antitumor properties of titanocene derivatives with thiophene containing ligands

The titanocene complexes [TiCp₂(Cl)R] (1), [TiCp₂(Cl)SR] (2), [TiCp₂(SR)₂] (3) with R = benzothienyl (BT) A and dibenzothienyl (DBT) B, were synthesized and the molecular structures of [TiCp₂(Cl)DBT] (1B) and [TiCp₂(Cl)SDBT] (2B) confirmed by single crystal X-ray diffraction studies. The dibenzothiophene rings are planar and for 1B in the plane of the titanium and chloro ligand. The chloro ligand is in a trans position to the sulfur atom with respect to the titanium-carbon bond. The complexes were studied for their electronic and structural features and preliminary tests were conducted for their tumor inhibiting properties against HeLa and COLO 320M tumor cell lines. These antitumor activities were compared against those observed for titanocene dichloride (S-01) under similar conditions and the highest antitumor activity was recorded for 2B.     

Synthesis and reactions of silicon containing cyclic α-amino acid derivatives

A simple synthesis of a new amino acid derivative 5,6-bis(trimethylsilyl)indanylglycine via cobalt mediated [2 + 2 + 2] cycloaddition strategy is described. Co-trimerization of diyne building block containing amino acid moiety with bis(trimethylsilyl)acetylene in presence of CpCo(CO)₂ catalyst afforded the silylated indane-based α-amino acid (AAA) derivative. Electrophilic aromatic substitution reaction, ipso to the trimethylsilyl group gave highly functionalised indane-based AAA derivatives.     

Synthesis of fluorinated glutamic acid derivatives via vinylalumination

A variety of structural types of fluorinated allylic acetates, prepared by vinylalumination of fluorinated aldehydes, were reacted with the benzophenone imine of glycine tert-butyl ester to provide 4-(fluorobenzylidenyl)- and 4-(fluoroalkylidenyl) glutamic acid derivatives in 61-96% yield. The 4-(4-fluorobenzylidenyl) glutamic acid derivative was hydrolyzed to give the 4-(4-fluorobenzylidenyl)pyroglutamate and then hydrogenated to the 4-(4-fluorobenzyl)pyroglutamate. The catalytic enantioselective conjugate addition-elimination of the benzophenone imine of glycine tert-butyl ester with the fluorinated allylic acetates prepared from fluoral, pentafluorobenzaldehyde, and 2,6-difluorobenzaldehyde provided the corresponding 4-(fluoroalkylidenyl)- and 4-(fluorobenzylidenyl) glutamic acid derivatives in 42, 45 and 80% ee, respectively.     

Synthesis and characterization of cyclometalated iridium(III) complexes containing benzoxazole derivatives and different ancillary ligands

The synthesis, structures, electrochemistry, and photophysics of a series of cyclometalated iridium(III) complexes based on benzoxazole derivatives and different β-diketonate ligands are reported. These complexes have a general formula C^∧N₂Ir(LL′) [where C^∧N is a monoanionic cyclometalating ligand; 2-phenylbenzoxazolato (pbo), 2-(4-chlorophenyl)benzoxazolato (cpbo), 2-phenyl-5-chlorobenzoxazolato (pcbo), 2-(3,5-difluorophenyl)benzoxazole (fpbo), or 2-(2-naphthyl)benzoxazolato (nbo), and LL′ is an ancillary ligand; acetylacetonate (acac), dibenzoylmethanate (dbm), or 1,1,1,5,5,5-hexafluoroacetylacetonate (hfacac)]. The complexes (pcbo)₂Ir(acac) (3), (dfpbo)₂Ir(acac) (4), (cpbo)₂Ir(dbm) (7), (dfpbo)₂Ir(dbm) (8), and (dfpbo)₂Ir(hfacac) (9) have been structurally characterized by X-ray crystallography. All of the complexes show reversible oxidation between 0.45 and 1.07 V, versus Fc/Fc⁺, and have short luminescence lifetime (τ = 0.1-1.3 μs) at room temperature. Except complex 9, the radiative decay rate (k_r) and nonradiative decay rate (k_nr) of the (C^∧N)₂Ir(LL′) complexes have been determined by using the lifetime and quantum efficiency. The k_r ranges between 2.0 × 10³ and 3.0 × 10⁵ s⁻¹ and k_nr spans a narrower range of values (5.0 × 10⁵ to 7.0 × 10⁶ s⁻¹).     

Synthesis and structural studies of peptides containing a glucose-derived furanoid sugar amino acid

Conformational analysis of peptides containing a glucose-derived furanoid sugar amino acid (Gaa) by detailed NMR and constrained MD studies revealed that peptides with repeating Gaa-Leu-Val units had conformational signatures very similar to those of linear homooligomers of Gaa.     

Synthesis and fungicidal activity of novel 1,2,4-triazole derivatives containing a pyrimidine moiety

Abstract

A series of novel 1,2,4-triazole derivatives containing a pyrimidine moiety were synthesized and their fungicidal activities were evaluated. The preliminary biological test indicated that some of the target compounds exhibited moderate to good fungicidal activities against the tested plant pathogenic fungi compared with the commercial agent. Among them, compounds 9n and 9o exhibited excellent antifungal activity against Phompsis sp., with the half-maximal effective concentration (EC₅₀) values of 25.4 and 31.6?μg/mL, which were even better than the commercial agent of Pyrimethanil (32.1?μg/mL). Meanwhile, compound 9o showed better fungicidal activities against B. dothidea and B. cinerea with 40.1 and 55.1?μg/mL, respectively, in comparison with that of commercial Pyrimethanil (57.6 and 62.8?μg/mL).     

Synthesis and characterization of poly(vinylcyclohexane) derivatives

Six nearly monodisperse substituted poly(styrene) homopolymers, poly(styrene) (PS), poly(2-methylstyrene) (P2MS), poly(3-methylstyrene) (P3MS), poly(4-methylstyrene) (P4MS), poly(tertiary-butylstyrene) (PtBS), and poly(α-methylstyrene) (FαMS) were anionically polymerized and subsequently saturated using heterogeneous hydrogenation techniques to poly(vinylcyclohexane) (PVCH), poly(2-methylvinylcyclohexane) (P2MVCH), poly(3-methylvinylcyclohexane) (P3MVCH), poly(4-methylvinylcyclohexane) (P4MVCH), and poly(tertiary-butylvinylcyclohexane) (PtBVCH), respectively. In each case, except PαMS, the materials were saturated to > 99% conversion with no chain degradation. PS hydrogenations required the addition of small amounts of tetrahydrofuran to the reaction solvent cyclohexane to enhance miscibility and eliminate large-scale chain degradation. Density gradient and differential scanning calorimetry (DSC) measurements were used to characterize the density and glass transition temperature, T_g, of the unsaturated and saturated polymers. Saturation reduces the density by 3% to 11% and changes T_g substantially. The greatest variation in T_g is obtained with the 3-methyl substituted species where a 63°C increase is observed, while the highest measured T_g is 186°C for P2MVCH. Small-angle neutron scattering (SANS) experiments on binary mixtures of hydrogenous and deuterium labeled PVCH derivatives provided a determination of bulk chain statistics. The statistical segment length is relatively insensitive to vinylcyclohexane ring substitution, except with P3MVCH where a 20% greater value is obtained. ©1995 John Wiley & Sons, Inc.     

Synthesis of substituted conformationally constrained 6,5- and 7,5-fused bicyclic lactams as dipeptide mimics

Using a convenient and practical route we report the preparation of a series of rigid surrogates of amino acids and dipeptides for application within constrained peptide analogues, and for employment as input for combinatorial science. These substituted 2-oxo-1-azabicycloalkane amino acids have the potential of replicating the backbone geometry and side-chain function of dipeptide residues like serine, lysine, glutamate, and related amino acids.     

Synthesis of jasplakinolide analogues containing a novel omega-amino acid

The synthesis of the omega-amino acid 4 is described utilizing a two-dimensional synthesis strategy combined with an enzymatic differentiation of homotopic ester groups. The amino acid 4 features two non-bonded interactions that result in conformational constraints on a cyclic construct. This amino acid was incorporated into the four macrolactams 17, 22, 31, and 37. The ring in 17 and 22 is 18-membered, whereas 31 and 37 have a 19-membered ring. The pairs with the same ring size differ in a N-methyl group. For the larger macrolactams (31 and 37) conformational analysis showed that the macrocyclic rings are somewhat more rigid than in the natural lead, the depsipeptide jasplakinolide. Nevertheless, their conformations are comparable to the natural product. There are no intramolecular hydrogen bonds, neither is the cis-rotamer populated in the N-methyl compound 37. Due to the increased flexibility of the smaller macrolactams 17 and 22 and signal overlap, a distinct solution structure could not be obtained for these compounds. The amino acid 4 should be useful for restricting the conformation of other small peptides.     

Synthesis and bioactivities of diamide derivatives containing a phenazine-1-carboxamide scaffold

Taking natural product phenazine-1-carboxamide (PCN) as a lead compound, a series of novel phenazine-1-carboxylic acid diamide derivatives were designed and synthesised. Their structures were confirmed by ¹H-NMR and HRMS. The bioassays showed that some of the target compounds exhibited promising in vitro fungicidal activities, and exhibited excellent and selective herbicidal activities. Particularly, compounds c, h, o and s displayed root length inhibition activities against barnyard grass with the rate of more than 80%. Compound c exhibited the best activity among all the target compounds against barnyard grass stalk length with the IC₅₀ value of 0.158 mmol/L, and compound o exhibited the best and wide spectrum inhibition against barnyard grass root length and rape in both root length and stalk length herbicidal activities with its IC₅₀ values of 0.067, 0.048 and 0.059 mmol/L respectively. The analysis of preliminary Structure-Activity Relationships provides the theoretical basis for further design of phenazine-1-carboxylic acid.     

苯并异硒唑酮氨基酸衍生物的合成及抗脂质过氧化作用

在已知具有氧化作用的2-苯基-1,2-苯并异硒唑-3(2H)-酮(Ebselen)的基础上, 将其2-位苯环更换成氨基酸乙酯, 设计并合成了9个苯并异硒酮的氨基酸衍生物3～11. 这类化合物的抗氧化作用药理研究表明,它们对Fe^2^+/半胱氨酸及维生素C诱发的大鼠肝微粒体脂质过氧化有抑制活性, 部分化合物活性比母体化合物Ebselen更优.     

Synthesis and properties of quinazoline derivatives containing cymantrenyl group

The synthesis of new quinazoline derivatives with 2,3- and 4-positioned cymantrenyl fragment is described. Alkylation of 2-substituted quinazolin-4-ones with cymantrenylalkyl bromides on using K₂CO₃, potassium tert-butoxide, and sodium hydride as bases has been studied. It is established for the first time that condensation of 2-methylquinazolin-4-ones with aldehydes can cause elimination of the substituent at the nitrogen atom in position 3. The new cymantrene derivatives possess fluorescence properties.     

Synthesis and characterization of trisubstituted heteropolytungstogermanates containing group 3A elements

Six new compounds, α,β-KaHb[GeW9M3(H2O)3O37].xH2O(M = Al, Ga,In; a + b =7) and α-K9H5[Ge2W18Ga6(H2O)3O74].20H2O, were synthesized from the lacunary precursors α and β-GeW9O34 10- and characterized by elemental analysis, spectroscopy and electrochemistry. Tungsten-183 NMR spectra of the title complexes consist of two lines with intensity ratio 2:1 as expected for trisubstituted heteropoly anions. The intensity ratio of α-Ga compound is 1:2, which is different from others(2:1). With the help of FAB mass spectrum, we concluded that it is a dimer with D3h, structure in aqueous, and the others exist by monomers with C3c structures.     

Synthesis and characterization of new 4,5-dihydropyrazol-1-yl derivatives

In this study, first, a series of chalcone compounds S1–S6 were synthesized from various acetophenone derivatives (acetophenone, p-methyl acetophenone, and p-methoxy acetophenone) and aromatic aldehyde derivatives (benzaldehyde, p-methyl benzaldehyde, and p-methoxy benzaldehyde) by the Claisen–Schmidt condensation reaction. These S1–S6 compounds were then used in the preparation of 4,5-dihydropyrazol-1-yl derivatives S7–S15. Finally, four new compounds S16–S19 were synthesized from compound (S7, S8, S9, and S12) and 2,4-dinitrophenylhydrazine. Therefore, three known and ten new heterocyclic compounds were synthesized and completely characterized using ¹H NMR, ¹³C NMR, IR, and elemental analysis.