Multiscale Modeling of Nanocrystalline Materials: A Variational Approach

This paper presents a variational multi-scale constitutive model in the finite deformation regime capable of capturing the mechanical behavior of nanocrystalline (nc) fcc metals. The nc-material is modeled as a two-phase material consisting of a grain interior (GI) phase and a grain boundary (GB) phase. A rate-independent isotropic porous plasticity model is employed to describe the GB phase, whereas a crystal-plasticity model which accounts for the transition from partial dislocation to full dislocation mediated plasticity is employed for the GI phase. Assuming the rule of mixtures, the overall behavior of a given grain is obtained via volume averaging. The scale transition from a single grain to a polycrystal is achieved by Taylor-type homogenization. It is shown that the proposed model is able to capture the inverse Hall-Petch effect. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Anticancer and anti-inflammatory sulfur-containing semisynthetic derivatives of sarcophine

Sarcophine (1), a cembranoid diterpene is known to inhibit the process of tumorigenesis. Sarcophine can be isolated in large amounts from the Red Sea soft coral Sarcophyton glaucum and hence is an ideal target for semisynthetic or biocatalytic modifications. Hydroxylated derivatives of 1 were reported to improve its anticancer activity. Despite the promising results and ready availability, there are limited attempts towards further diversifying the library of sarcophine derivatives. Hence, the current study targets the epoxide ring to generate sulfur-containing derivatives of sarcophine by reacting it with ammonium thiocyanate and Lawesson's reagent. Structure elucidation of the products was based on extensive 1D and 2D NMR and high resolution mass spectrometry, in addition to mechanistic considerations. The effect of these derivatives on highly malignant +SA mammary epithialial cell proliferation is reported. Anti-inflammatory potential of sarcophine and its derivatives is also demonstrated.     

Chiral Monolithic Silica-Based HPLC Columns for Enantiomeric Separation and Determination: Functionalization of Chiral Selector and Recognition of Selector-Selectand Interaction

This review draws attention to the use of chiral monolithic silica HPLC columns for the enantiomeric separation and determination of chiral compounds. Properties and advantages of monolithic silica HPLC columns are also highlighted in comparison to conventional particle-packed, fused-core, and sub-2-µm HPLC columns. Nano-LC capillary monolithic silica columns as well as polymeric-based and hybrid-based monolithic columns are also demonstrated to show good enantioresolution abilities. Methods for introducing the chiral selector into the monolithic silica column in the form of mobile phase additive, by encapsulation and surface coating, or by covalent functionalization are described. The application of molecular modeling methods to elucidate the selector–selectand interaction is discussed. An application for enantiomeric impurity determination is also considered.     

Thermal Stability of Modified i‐Motif Oligonucleotides with Naphthalimide Intercalating Nucleic Acids

In continuation of our investigation of characteristics and thermodynamic properties of the i‐motif 5′‐d[(CCCTAA)₃CCCT)] upon insertion of intercalating nucleotides into the cytosine‐rich oligonucleotide, this article evaluates the stabilities of i‐motif oligonucleotides upon insertion of naphthalimide (1H‐benzo[de]isoquinoline‐1,3(2H)‐dione) as the intercalating nucleic acid. The stabilities of i‐motif structures with inserted naphthalimide intercalating nucleotides were studied using UV melting temperatures (T_m) and circular dichroism spectra at different pH values and conditions (crowding and non‐crowding). This study indicated a positive effect of the naphthalimide intercalating nucleotides on the stabilities of the i‐motif structures compared to the wild‐type structure which is in contrast to a previous observation for a pyrene‐intercalating nucleotide showing a decrease in T_m values.     

Synthesis,Antiviral, and Antimicrobial Activity of N‐ and S‐Alkylated Phthalazine Derivatives

A series of N‐alkylphthalazinone were synthesized by the reaction of phthalazin‐1(2H)‐one derivatives 1a , 1b , 1c with alkylating agents namely, propargyl, allyl bromide, epichlorohydrin, 1,3‐dichloro‐2‐propanol, 4‐bromobutylacetate, and 1‐(bromomethoxy)ethyl acetate to give the corresponding N‐alkylphthalazinone 2a , 2b , 2c , 3a , 3b , 3c , 5a , 5b , 5c , 6a , 6b , 6c , 7a , 7b , 7c , and 9a , 9b , 9c . Alkylation of phthalazin‐1(2H)‐thione to give a series from S‐alkylphthalazine 12 , 13 , 14 and thioglycosides 15 and 17 was performed. Deprotection of compounds 7a , 7b , 7c , 9a , 9b , 9c , 15 , and 17 resulted in the formation of the corresponding products 8a , 8b , 8c , 10a , 10b , 10c , 16 , and 18 . The structure of newly synthesized compounds was assigned by IR, ¹H, ¹³C NMR, and elemental analysis. Some of these compounds were screened for antiviral and antimicrobial activity.     

Phytochemical analysis, cytotoxic activity and constituents-activity relationships of the leaves of Cinnamomum iners (Reinw. ex Blume-Lauraceae)

The leaves of Cinnamomum iners (Reinw. ex Blume-Lauraceae) have been refluxed successively with chloroform and alcohol to get chloroform extract and alcoholic extract. Both the extracts have been assayed for cytotoxicity against human colorectal tumour cells. The chloroform extract exhibited significant cytotoxicity with IC(50) 31?μg mL(-1) (p??200?μg mL(-1). The chloroform extract has been further proceeded for chemical analysis by GC-TOFMS and 178 components were identified including acids, amines, amides, aldehydes, alcohols, esters, benzene derivatives, bicyclic compounds, terpenes, hydrocarbons, naphthalene derivatives, furan derivatives, azulenes, etc. Nine components representing 51.73% of the total chloroform extract were detected as major components. Caryophyllene (14.41%) and Eicosanoic acid ethyl ester (12.17%) are the most prominent components of the chloroform extract. β-Caryophyllene (14.41%) as most abundant compound supports potent cytotoxicity as shown by chloroform extract.     

Preparation of some chitosan heavy metal complexes and study of its properties

The chitosan was prepared and mixed with some metal salts (FeCl₃, Co(OAc)₂ and NiCl₂) by different concentrations to form chitosan-metal complexes. The metal ions which strongly complexed to the amino groups of chitosan like Fe showed a smooth surface product, amorphous phase, thermally more stable and high electrical conductivity than other complexes, while the Co ions which the weakly complexed with chitosan showed a rough surface product, crystalline phase, thermally less stable and low electrical conductivity. The chitosan-metal complexes have a higher electrical conductivity than chitosan pure at room temperature.     

Immobilized dimeric chiral Mn(III) salen complex on short channel ordered mesoporous silica as an effective catalyst for the epoxidation of non-functionalized alkenes

Chiral dimeric Mn(III) salen complex with 1R, 2R-(?)-diaminocyclohexane collar was immobilized on short channel large pore sized silica through a long linker of {(CH₂)₃–NH–melamine–piperazine} to investigate its performance in enantioselective epoxidation of chromenes, indene, styrene and cis β-methyl styrene in the presence of pyridine N-oxide (PyNO) as an axial base using aqueous NaOCl as an oxidant at 0 °C. The immobilized catalyst system showed high turnover frequency (TOF) and enantioselectivity for the smaller and bulkier alkenes like styrene, indene, 2,2-dimethylchromene and 6-cyano-2,2-dimethylchromene (ee up to 98%). These results are the best reported for heterogeneous catalyst under biphasic reaction conditions and were comparable to the dimeric Mn(III) salen system under homogeneous condition. The performance of the immobilized catalyst was retained for six reuse experiments. This protocol was extended to the synthesis of an antihypertensive drug (S)-Levchromakalim (ee 98%) at 1 g level.     

Synthesis and Antimicrobial Activity of New 1,2,3‐Triazolopyrimidine Derivatives and Their Glycoside and Acyclic Nucleoside Analogs

New [1,2,4‐oxadiazolyl]methyl‐3H‐[1,2,3]triazolo[4,5‐d]pyrimidin derivatives were synthesized starting from N′‐Hydroxy‐1‐naphthimidamide. The N‐substituted acyclic nucleoside analogs as well as the substituted glycosides were also prepared by reaction with the corresponding reagents. The antimicrobial results indicated that most of the tested compounds exhibited moderate to high antimicrobial activity whereas few compounds were found to exhibit little or no activity against the tested microorganisms.     

Synthesis and antimicrobial activity of substituted [(pyrazol‐4‐yl)methylene]hydrazono‐2,3‐dihydrothiazoles and their sugar derivatives

A number of new [(pyrazol‐4‐yl)methylene]hydrazono‐2,3‐dihydrothiazole derivatives, their sugar hydrazones and N‐glycosides were synthesized. Furthermore, N‐substituted oxygenated alkyl and hydroxyl derivatives and 1,3,4,‐oxadiazoline acyclic nucleoside analogs were prepared. The newly synthesized compounds were tested for their antimicrobial activities and showed moderate to high inhibition activities. J. Heterocyclic Chem., (2012).