Synthesis and transdermal permeation of novel N4-methoxypoly(ethylene glycol) carbamates of cytarabine

Background: Cytarabine is a deoxycytidine analogue commonly used in the treatment of hematological malignant diseases. Its clinical utility, however, is severely limited by its short plasma half-life because of the catabolic action of nucleoside deaminases. Method: In this study, N⁴-carbamate derivatives of cytarabine (1) were synthesized and evaluated for transdermal penetration because this mode of administration may circumvent its limitations. The synthesis of these compounds was achieved in a two-step process. First, the methoxypoly(ethylene glycol) was activated by p-nitrophenyl chloroformate. Second, the activated intermediates were reacted with cytarabine in the presence of N-hydroxysuccinamide to give the N⁴-methoxypoly(ethylene glycol) carbamate derivatives. The transdermal flux values of the N⁴-carbamates of cytarabine were determined in vitro by Franz diffusion cell methodology. Aqueous solubility and log D (pH 7.4) values were determined and assessed for correlation with transdermal flux values. Results: The synthesized carbamates, particularly, (9)–(13), showed increased solubility in both aqueous and lipid media. Log D values decreased as the oxyethylene chain lengthened. Conclusion: Although none of the derivatives showed significantly higher transdermal penetration than cytarabine (1), it should be mentioned that the mean for cytarabine N⁴-methoxyethyleneoxycarbamate (8) was 10 times higher and the median was 2 times higher.     

Carbazole based hole transporting materials for solid state dye sensitizer solar cells: role of the methoxy groups

The synthesis of new organic hole transporting materials (HTMs) based on 3,6‐disubstituted 9H‐carbazole‐3,6‐diamine,N,N,N′,N′‐tetraphenyl‐9‐(4‐methoxyphenyl) derivatives and their applications in solid state dye sensitizer solar cells (DSSCs) are described. The effect of the methoxy group localized on the para position of the diphenylamine moieties on the thermal, electronic and electrochemical properties and photovoltaic performance is discussed. In solid state DSSCs, utilization of the aforementioned HTMs in combination with the dye D102 (TiO₂/D102/HTM/Au) shows a positive influence of the methoxy group on the photovoltaic conversion efficiency compared with unsubstituted diphenylamine grafted groups. A study on the concentration of the HTM is also carried out and shows an optimal concentration around 200 mg mL^?1. Without further optimization, the best device gives a power conversion efficiency of 1.75% under AM 1.5 solar irradiation (100 mW cm^?2).     

Electrochemical characterization of alternate conducting carbazole-bisthiophene units

An electrochemical and theoretical character of alternate copolymer of carbazole and bithiophene units was investigated. Polymerization is processed as two steps bielectronic oxidation of molecule. With monoelectronic oxidation is connected stable radical cation with spin located mainly on carbazole. The electrochemical properties of polymer are dependent on thickness of film deposited on electrode. In case of the thin layers one it is observed characteristic redox couple of carbazole oxidation to radical cation. Analysis of polymer behavior and results of spectrochemical measurements indicate on mixed type of electroconductivity.Molecular structures, HOMO-LUMO gaps and nature of highest occupied and lowest unoccupied molecular orbitals were also studied in presented work for oligomers ranging from monomer to octamer. The studies applied density functional theory (DFT).     

Potential Use of Ascorbic Acid–Based Surfactants as Skin Penetration Enhancers

ABSTRACT

6-O-Ascorbic acid alkanoates (ASCn) are amphiphilic molecules having physical-chemical properties that depend on the alkyl chain length. The derivatives of low molecular weight (n < 11) have enough aqueous solubility to produce self-assemblies at room temperature (≈25°C), while those with longer alkyl chains possess a critical micellar temperature (CMT) higher than 30°C. At higher temperatures (T° > CMT), ASCn aqueous suspensions turn into either micellar solutions or gel phases, depending on the length of the hydrophobic chain. On cooling, coagels are produced, which possess a lamellar structure that exhibit sharp X-ray diffraction patterns and optical birefringence. The semisolid consistency of such coagels is an interesting property to formulate dermatological pharmaceutical dosage forms able to solubilize and stabilize different drugs. The objective of the present study was the evaluation of the enhancing permeation effect of ASCn with different chain lengths and to correlate permeability changes with histological effects. With this purpose, ASCn coagels containing anthralin (antipsoriasic drug) or fluorescein isothiocyanate (FITC, hydrophobic fluorescent marker) were assayed on rat skin (ex vivo) and mice skin (in vivo), respectively. Also, histological studies were performed aimed at detecting some possible side effects of ASCn. No inflammatory cellular response was observed in the skin when ASCn coagels were applied, suggesting non-irritating properties. Light microscopy indicated slight disruption and fragmentation of stratum corneum. The penetration of ASCn through rat skin epidermis was very fast and quantitatively significant. The permeation of anthralin was significantly increased when the drug was vehiculized in ASCn coagels, compared to other pharmaceutical systems. The results indicated that ASC12 seems to have the highest enhancing effect on FITC permeation. ASC12 appears to be the compound that possesses the highest capacity to enhance the penetration of the drugs. Furthermore, it has the highest permeation of the serie.     

Theoretical study of charge transfer mechanism in fullerene-phenyl-phenothiazine compound: A real-space analysis

Quantum chemistry methods as well as two-dimensional (2D) and three-dimensional (3D) real-space analysis have been conducted to study the photo-induced intramolecular charge-transfer (ICT) and excited state properties of fullerene-phenylphenothiazine, which has recently been developed for solar cells. Firstly, we obtained the energy levels and spatial distributions of HOMO/LUMO, energy gap (ΔEH-L) and excitation energies on the basis of quantum chemistry study. Secondly, two-dimensional (2D) and three-dimensional (3D) real-space analysis were used to visualize the CT process and to reveal the nature of the excited states. In the above analyses, the 2D real-space analysis of the transition density matrix provided information about the electron-hole coherence, and the 3D real-space analysis of charge difference density enabled the visualization of the orientation and result of the ICT. The results of real-space analysis directly indicate that some states are ICT states, and others belong to locally excited states. Moreover, according to the generalized Mulliken Hush theory, we calculated the electronic coupling matrix elements and predict that electron transfer for some ICT states more easily takes place than that for some locally excited states.     

Novel A-D-A type small molecules with β-alkynylated BODIPY flanks for bulk heterojunction solar cells

A serial of novel A-D-A type small molecules with BODIPY linked through alkynyl with various electron donor units such as fluorene, carbazole, benzodithiophene and phenothiazine, namely F-BDP, C-BDP, B-BDP and P-BDP, respectively, were designed and synthesized. Introducing the alkynyl bridge leads to extending the molecular absorption spectrum to the range of 320–700 nm with high molar extinction coefficients (10⁵ cm⁻¹ M⁻¹) and strong fluorescence quenching. The molecules showed relatively low HOMO ranging from −5.02 to −5.24 eV as estimated from cyclic voltammetry measurements. Interestingly, B-BDP with BDT as donor exhibits more obviously red-shifted absorption in the solid state compared to F-BDP, C-BDP and P-BDP. Furthermore, the solution-processed bulk-heterojunction organic solar cell based on B-BDP/PC₇₁BM present superior charge transport property and more favorable nanoscale morphology, resulting in a significant higher J_sc of 11.84 mA cm² and FF than the other counterparts, thus achieved a higher PCE of 4.65%, which is one of the best values among the ever reported BODIPY based organic solar cells.     

Role of geometry, substrate and atmosphere on performance of OFETs based on TTF derivatives

We report a comparative study of OFET devices based on zone-cast layers of three tetrathiafulvalene (TTF) derivatives in three configurations of electrodes in order to determine the best performing geometry. The first testing experiments were performed using SiO₂/Si substrates. Then the optimum geometry was employed for the preparation of flexible OFETs using Parylene C as both substrate and dielectric layer yielding, in the best case, to devices with μ_FET = 0.1 cm²/V s. With the performed bending tests we determined the limit of curvature radius for which the performance of the OFETs is not deteriorated irreversibly. The investigated OFETs are sensitive to ambient atmosphere, showing reversible increase of the source to drain current upon exposition to air, what can be explained as doping of TTF derivative by oxygen or moisture.     

High efficiency OLEDs based on anthracene derivatives: The impact of electron donating and withdrawing group on the performance of OLED

New well-defined bulky anthracene derivatives with side groups having electron donating or withdrawing properties 8a-d were synthesized. The compounds contain substituted anthracene as the central core attaching 2-(4-(2-pyridinyl)- phenyl)vinyl and 4-R-phenyl [R: H (a), OMe (b) and CF₃ (c), N(Ph)₂ (d)] groups at 9- and 10- positions. The impact of electron donating, withdrawing and neutral groups and their influence on the molecules photophysical, charge transfer (CT), triplet transfer (TT) and triplet–triplet annihilation (TTA) properties has been investigated. Based on the photophysical studies the most promising molecule (8d) has been selected and high efficiency fluorescent OLEDs with EQE at very low current efficiency reaching 7% were obtained. The value at low current density implies a Triplet Fusion (TF) contribution of 45%, very close to the maximum theoretical value of 50% when only the singlet decay channel is open to TTA, however we believe that in this case both TTA and TADF contribute to the triplet harvesting to yield high EQE values, and this mixed triplet harvesting arises through the heterogeneity of the films. At high current density a brightness of 20000 cd/m² was achieved and it is assigned partially to the material crystallisation.     

2-(2-吡啶)-5,6,7,8-四氢吡啶并[4,3-d]嘧啶及其衍生物的合成

以N-叔丁氧羰基-4-哌啶酮为原料,设计合成了一种新型的2-(2-吡啶)-5,6,7,8-四氢吡啶并[4,3-d]嘧啶及其3种衍生物,通过~1HNMR、LC-MS和HPLC确证了3种衍生物的结构。实验证明,所合成的3种衍生物能够高效抑制白血病K562细胞系的增殖,同时能够有效抑制卵巢癌HO-8910细胞的增殖。     

Perfluoropolyether polymers by UV curing: design,synthesis and characterization

Perfluoropolyether (PFPE) structures can be functionalized with acrylic groups using appropriate hydrogenated acrylic monomers: the macromers obtained are highly reactive under UV irradiation, and fluorinated polymers can be obtained. In the first part of this work is described the synthesis of new PFPE (meth)acrylic oligomers by extending OH‐terminated fluorinated chains with urethane groups and reactive acrylic functions. The photopolymerization reaction of each product is then reported followed by the characterisation of the main thermal, mechanical and surface properties of UV‐cured coatings. The polymers have good thermal resistance and fair mechanical and chemical resistance. More interestingly they show very low refractive index and low surface tension. For these latter properties the products can be advantageously used in highly demanding applications such as photonic devices and nano‐patterning. Copyright © 2011 Society of Chemical Industry