One‐Pot Three‐Component Synthesis of α‐Amino Nitriles Catalyzed by 2,4,6‐Trichloro‐1,3,5‐triazine (Cyanuric Acid)

A simple and efficient method has been developed for the synthesis of α‐amino nitriles from aldehydes, amines and trimethylsilyl cyanide (Me₃SiCN) in the presence of a catalytic amount of cyanuric acid at room temperature.     

The First Stereoselective Total Synthesis of a Naturally Occurring Bioactive Diarylheptanoid, (3R,6E)‐1,7‐Bis(4‐hydroxyphenyl)hept‐6‐en‐3‐ol,through Two Different Approaches

The stereoselective total synthesis of a naturally occurring bioactive diarylheptanoid, (3R,6E)‐1,7‐bis(4‐hydroxyphenyl)hept‐6‐en‐3‐ol, has been accomplished starting from 4‐hydroxybenzaldehyde through two different approaches involving Wittig olefination, hydrolytic kinetic resolution of a racemic epoxide, and olefin cross‐metathesis reaction as the key steps.     

Multiporphyrin arrays on cyclophosphazene scaffolds: synthesis and studies

The stable and robust cyclotriphosphazene and cyclotetraphosphazene rings were used as scaffolds to prepare hexa- and octaporphyrin arrays by treating N(3)P(3)Cl(6) and N(4)P(4)Cl(8), respectively, with 5-(4-hydroxyphenyl)-10,15,20-tri(p-tolyl)porphyrin (N(4) core) or with its thiaporphyrin analogues (N(3)S and N(2)S(2) cores) in THF in the presence of Cs(2)CO(3) under simple reaction conditions. Thiaporphyrins were examined in addition to the normal porphyrin to tune the electronic properties of the resultant arrays. Observation of the molecular ion peaks in the mass spectra confirmed the molecular structures of the arrays. 1D and 2D NMR techniques were employed to characterize the multiporphyrin arrays in detail. The (1)H NMR spectra of the multiporphyrin arrays each show a systematic set of signals, indicating that the porphyrin units are arranged in a symmetrical fashion around the cyclophosphazene rings. All signals in the (1)H NMR spectra were assigned with the aid of COSY and NOESY experiments. The protons of each porphyrin unit are subject to upfield and downfield shifts because of the ring-current effects of neighboring porphyrin units. Optical, electrochemical, and fluorescence studies of the arrays indicated that the porphyrin units retain their independent ground- and excited-state characteristics. Cu(II) and Ni(II) derivatives of hexaporphyrin and octaporphyrin arrays containing N(4) porphyrin units and N(3)S porphyrin units were synthesized, and complete metalation of the arrays was confirmed by their mass spectra and by detailed NMR characterization of the Ni(II) derivatives of hexa- and octaporphyrin arrays containing N(4) porphyrin units. Electrochemical studies indicated that Cu(II) and Ni(II) ions present in the thiaporphyrin units of the arrays can be stabilized in the +1 oxidation state, which is not possible with arrays containing normal porphyrin units.     

Optimization of biodiesel production in a hydrodynamic cavitation reactor using used frying oil

The present work demonstrates the application of a hydrodynamic cavitation reactor for the synthesis of biodiesel with used frying oil as a feedstock. The synthesis involved the transesterification of used frying oil (UFO) with methanol in the presence of potassium hydroxide as a catalyst. The effect of geometry and upstream pressure of a cavitating orifice plate on the rate of transesterification reaction has been studied. It is observed that the micro level turbulence created by hydrodynamic cavitation somewhat overcomes the mass transfer limitations for triphasic transesterification reaction. The significant effects of upstream pressure on the rate of formation of methyl esters have been seen. It has been observed that flow geometry of orifice plate plays a crucial role in process intensification. With an optimized plate geometry of 2 mm hole diameter and 25 holes, more than 95% of triglycerides have been converted to methyl esters in 10 min of reaction time with cavitational yield of 1.28 × 10^?3 (Grams of methyl esters produced per Joule of energy supplied). The potential of UFO to produce good quality methyl esters has been demonstrated.     

MS2/TOF and LC-MS/TOF studies on toremifene to characterize its forced degradation products

The present study was designed to characterize the possible degradation products of toremifene under varied conditions as prescribed by ICH guidelines Q1A(R2). The forced degradation studies were conducted on toremifene citrate under the conditions of hydrolysis (acidic, basic and neutral), photolysis, oxidation and dry heat. The drug was found unstable to photolysis and hydrolysis in water and acidic media but stable to alkaline hydrolysis, peroxide oxidation and thermal degradation. In total fifteen degradation products (I-XV) were formed, which were resolved from each other and the drug on a C-18 column employing an isocratic elution method. A complete mass fragmentation pattern of the drug was established with the help of LC/ESI-MS/TOF to assist characterization of the degradation products. Of the fifteen products, six products III, IV, VII, VIII, XIV and XV were detected in LC-MS. The molecular masses of III, IV, VII and VIII were found to be the same i.e., 387, while those of XIV and XV were 389 and 403, respectively. Structures of these products were elucidated through comparison of their mass fragmentation patterns with the drug, which were proposed on the basis of accurate masses of the parent and fragment ions. These were characterized as (Z)-2-(2-(dimethylamino)ethyl)-4-(4-hydroxy-1,2-diphenylbut-1-enyl)phenol (III), (E)-2-(2-(dimethylamino)ethyl)-4-(4-hydroxy-1,2-diphenylbut-1-enyl)phenol (IV), (E)-4-(4-(2-(dimethylamino)ethoxy)phenyl)-3,4-diphenylbut-3-en-1-ol (VII), (Z)-4-(4-(2-(dimethylamino)ethoxy)phenyl)-3,4-diphenylbut-3-en-1-ol (VIII), 2-(4-(10-(2-chloroethyl)phenanthren-9-yl)phenoxy)-N-methylethanamine (XIV), and 2-(4-(10-(2-chloroethyl)phenanthren-9-yl)phenoxy)-N,N-dimethylethanamine (XV). Finally, a most plausible mechanistic explanation for degradation of the drug in different chemical environments is also proposed. The results of the study disclose six new degradation related impurities of the drug.     

Bifunctional binding of cisplatin to DNA: why does cisplatin form 1,2-intrastrand cross-links with ag but not with GA?

The bifunctional binding of the anticancer drug cisplatin to two adjacent nucleobases in DNA is modeled using density functional theory. Previous experimental studies revealed that cisplatin binding to adjacent guanine and adenine is sensitive to nucleobase sequence. Whereas AG 1,2-intrastrand cross-links are commonly observed, the analogous GA adducts are not known. This study focuses on understanding this directional preference by constructing a full reaction profile using quantum chemical simulation methods. Monofunctional and bifunctional cisplatin adducts were generated, and the transition states that connect them were located for the dinucleotides d(pApG) and d(pGpA), assuming that initial platination takes place at the guanine site. Our computer simulations reveal a significant kinetic preference for formation of the AG over the GA adduct. The activation free energies of approximately 23 kcal/mol for AG and approximately 32 kcal/mol for GA suggest that bifunctional closure is approximately 6 orders of magnitude faster for AG than for GA. A strong hydrogen bond between one of the ammine ligands of cisplatin and the 5' phosphate group of the DNA backbone is responsible for the stabilization of the transition state that affords the AG adduct. This interaction is absent in the transition state that leads to the GA adduct because the right-handed helix of the DNA backbone places the phosphate out of reach for the ammine ligand. We found only an insignificant thermodynamic difference between AG and GA adducts and conclude that the preference of AG over GA binding is largely under kinetic control. The puckering of the deoxyribose ring plays an important role in determining the energetics of the bifunctional platination products. Whereas the 3'-nucleoside remains in the native C2'-endo/C3'-exo form of B-DNA, the deoxyribose of the 5'-nucleoside always adopts the C2'-exo/C3'-endo puckering in our simulations. A detailed analysis of the energies and structures of the bifunctional adducts revealed that the observed sugar puckering patterns are necessary for platinum to bind in a relaxed coordination geometry.     

A New Conformationally Symmetrical Calix[4]pyrrole Based Supramolecular System for Liquid Crystalline and Window Layer Solar Cell Applications

The newly symmetrical liquid crystalline compounds (CPB₁ – CPB₄) based on calix[4]pyrrole as central rigid core are synthesized via esterification reaction. All the four functionalized compounds exhibit columnar hexagonal phase (Col_h) over a higher mesophase temperature range and further stabilized mesophase upto room temperature. The thermal behavior and optical texture are identified by using differential scanning calorimetry (DSC), Polarizing optical microscopy (POM) while the molecular organization of compound in mesogenic state by X-ray diffraction technique. The molecular system based on calix[4]pyrrole core with symmetrical nature exhibited columnar type self-assembly at room temperature. All these four supramolecules with different side spacer show higher thermal stability. Based upon the optimization, compound CPB₂ has been further tested to implicate as optical window layer in thin films solar cell devices. The calix[4]pyrrole functionalized supramolecular liquid crystalline compound based thin films showed suitable transmittance, optical energy band gap together with absorbance and extinction coefficient. The linear dependence of current on the voltage demonstrated Ohmic behavior of the CPB₂ films. The surface morphology to the developed samples designated nearly uniform deposition of the CPB₂ thin films together with grain growth. The findings warrant suitability of the films to implicate these as an eco-friendly optical window layer in thin films based solar cells.     

Indium Trichloride Catalyzed Diels–Alder Reaction: Synthesis of Novel 5‐Butyl‐11a‐aryl‐4a,5,11,11a‐tetrahydro‐11bH‐indolo[3,2‐c]quinoline‐1,4‐dione

Hetero Diels–Alder reaction of 3‐butyliminomethyl‐2‐aryl‐1H‐indoles (Schiff's base) 1 with p‐benzoquinone 2 affords six novel 5‐butyl‐11a‐aryl‐4a,5,11,11a‐tetrahydro‐11bH‐indolo[3,2‐c]quinoline‐1,4‐diones 3 in good yields. All the reactions proceeded with complete diastereoselectivity giving only one product in each case, which was characterized on the basis of its elemental analyses and spectral data (IR, ¹H NMR, and Mass).     

Stereoselective synthesis of the lichen metabolite, (+) montagnetol and its congeners as antimicrobial agents

Abstract

In view of structural diversity, (+) montagnetol, the major metabolite of the fruticose lichen, Roccella montagnei was synthesized along with three of its congeners by employing highly efficient protocols. (+) Montagnetol (2?R, 3S; 11) and (-) montagnetol (2S, 3R; 5) were synthesized in 7 and 9 steps, respectively, from L-ascorbic acid. The two new congeners 3 (2?R, 3R) and 6 (2S, 3S), which differ in configuration at C-2 and C-3 positions of the (+) montagnetol, were synthesized from (?) diethyl D-tartrate and (+) diethyl L-tartrate, respectively. The synthesized compounds were evaluated in vitro for antimicrobial activity against two Gram-positive (S. aureus and E. coli) and two Gram-negative (S. typhi and P. aeruginosa) bacteria and one fungal strain Candida albicans. Interestingly, the congener 3 showed promising anti-bacterial activity (MIC: 0.062?µg/ml) against P. aeruginosa, whereas the congener 6 displayed potent anti-fungal activity (MIC: 0.062?µg/ml) against C. Albicans.