Stepwise Assembly of [(C5H5)4(C5Me5)4Co4Rh4(CN)12]4+, an “Organometallic Box”

A volume of 132 Å ³ is enclosed by the title compound 1 , which thus offers plenty of room for potential guest molecules. The synthesis from 2 [{Cp*RhCl₂}₂] and 4 [CpCo(CN)₃]⁻ begins with the construction of a “molecular square” whose corners are alternately occupied by Co and Rh centers. Two squares react with one another to give a “molecular box” without cleavage of any M–C bonds. Cp=C₅H₅, Cp*=C₅Me₅.     

An “One-Pot” Synthesis of Substituted 3-Benzoylamino-5-oxo-5, 6, 7, 8-Tetrahydrocoumarins

A new simple “one-pot” synthesis of some 3-benzoylamino-5-oxo-5, 6, 7, 8-tetrahydrocoumarins from 1, 3-cyclohexanediones, hippuric acid, acetic anhydride and triethyl orthoformate or other one-carbon synthetic equivalent is described.     

On triazoles. XXXIX. Synthesis and structure of some 1,2,4-triazolo[1,5-a]pyrimidin-5-one oximes

Some 1,2,4-triazolo[1,5-a]pyrimidin-5-one derivatives 1 and their alicyclic condensed ring analogues 2-3 were converted through the corresponding “imino chlorides” 4-6 to the oximes 7-9 . The “E” isomeric structure of the products obtained was proven with the use of cmr using the spectral data of the corresponding “benzyloximino” derivatives 10-12 prepared as model compounds.     

The role of human C5a as a non-genomic target in corticosteroid therapy for management of severe COVID19

Complement system plays a dual role; physiological as well as pathophysiological. While physiological role protects the host, pathophysiological role can substantially harm the host, by triggering several hyper-inflammatory pathways, referred as “hypercytokinaemia”. Emerging clinical evidence suggests that exposure to severe acute respiratory syndrome coronavirus-2 (SARS-CoV2), tricks the complement to aberrantly activate the “hypercytokinaemia” loop, which significantly contributes to the severity of the COVID19. The pathophysiological response of the complement is usually amplified by the over production of potent chemoattractants and inflammatory modulators, like C3a and C5a. Therefore, it is logical that neutralizing the harmful effects of the inflammatory modulators of the complement system can be beneficial for the management of COVID19. While the hunt for safe and efficacious vaccines were underway, polypharmacology based combination therapies were fairly successful in reducing both the morbidity and mortality of COVID19 across the globe. Repurposing of small molecule drugs as “neutraligands” of C5a appears to be an alternative for modulating the hyper-inflammatory signals, triggered by the C5a-C5aR signaling axes. Thus, in the current study, few specific and non-specific immunomodulators (azithromycin, colchicine, famotidine, fluvoxamine, dexamethasone and prednisone) generally prescribed for prophylactic usage for management of COVID19 were subjected to computational and biophysical studies to probe whether any of the above drugs can act as “neutraligands”, by selectively binding to C5a over C3a. The data presented in this study indicates that corticosteroids, like prednisone can have potentially better selectively (K_d ∼ 0.38 μM) toward C5a than C3a, suggesting the positive modulatory role of C5a in the general success of the corticosteroid therapy in moderate to severe COVID19.     

Synthesis of a new class of acyclic 2′,5′- and 3′,5′-oligonucleotide analogs based on 9-[1,5-dihydroxy-4(S)-hydroxymethyl-3-oxapent-2(R)-yl]-adenine

The acyclic analogs of 2′,5′- and 3′,5′-oligoadenylates possessing all functional groups of the natural compounds were prepared on the basis of “oxydized-reduced” adenosine.     

Bioactive principles in exudate gel from the leaf of Aloe fleurentiniorum,traditionally used as folkloric medicine by local people of Aridah and Fayfa mountains,Saudi Arabia

Aloe fleurentiniorum is a desert plant that is occasionally used to treat wounds by local people of Aridah and Fayfa mountains in Saudi Arabia. However, medicinal value of the plant has not been scientifically established. The purpose of this study was to determine the bioactive phytocomponents contained in the exudate gel (EG) from the leaves of Aloe fleurentiniorum using GC–MS and FT-IR studies, as well as antibacterial assays. Medicinally important bioactive compounds were identified using GC–MS analysis. The bioactive compounds are “pregn-5-ene-3α,20-diol”, “16α-methyl-pregnane-11,20-dione”, “3-hydroxy-(3α,5α)-, ursodeoxycholic acid”, “1-heptatriacotanol”, “allopregnane-7α,11α-diol-3,20-dione”, “D-arabino-hexopyranoside”, “2-octadecenoic acid methyl ester”, “D-ribo-hexose,2,6-dideoxy-3-O-methyl glucosamine”, “N-acetyl-N-benzoyl-alpha-D-glucopyranoside”, “nonyl 1-thio pregnenolone”, “5-cholestene-3-ol, 24-methyl-cholestanol”, and “D-allose hexadecanoic acid methyl ester”. Furthermore, specific groups and their respective chemical compounds were identified via FT-IR spectroscopy studies. The FT-IR spectroscopy of EG showed various functional groups at 3354, 2945, 2832, 2523, 2046, 1707, 1451, 1108, 1031, 880, 737 and 610 cm⁻¹. The FT-IR peaks revealed the likely presence of various compounds such as glycosides, flavonoids, steroids, saponins, flavonoids, amino sugars, cutin and isothiocyanate. Moreover, EG produced a wide range of antibacterial effects on some screened human pathogenic bacteria.     

On the mechanism of the ion-molecule reaction CH3+ + CH4 = C2H5+ + H2

Experimental evidence supporting the “direct” reaction model and the “intermediate complex” model for the reaction CH₃⁺(CH₄, H₂)C₂H₅⁺ are analysed. It is shown that the evidence for the former can equally well be interpreted in terms of a proposed model of persistent complex formation and decay. The plausibility of a “direct” mechanism is discussed and is found to be poor.     

Synthesis and Electrochromic Properties of Star‐Shaped Oligomers with Phenyl Cores

A series of star‐shaped conjugated oligomers, 1,3,5‐tri(2′‐thienyl) benzene (3TB), 1,3,5‐tri(3′,4′‐ethylenedioxythienyl) benzene (3EB), 1,3,5‐tri[5′,2“‐(3”,4“‐ethylenedioxy‐thienyl)‐2′‐thienyl] benzene (3ETB), and 1,3,5‐tri[5′,2”‐(3“,4”‐ethylenedioxy‐thienyl)‐2′‐thienyl]‐4‐(3′,4′‐ethylenedioxythienyl)benzene (3TB‐4EDOT), were synthesized. The star‐shaped polymer, poly(1,3,5‐tri[5′,2“‐(3”,4“‐ethylenedioxythineyl)‐2′‐thienyl]benzene) (P3ETB), was also prepared. The electrochemical and electrochromic properties of these conjugated oligomers and polymer were investigated. These oligomer and polymer films showed reversible, clear color changes upon electrochemical doping and dedoping. The color of the P3ETB film reversibly changed from orange to blue under doping and dedoping. The switching times for doping and dedoping were 1.2 and 0.9 s, respectively.     

Novel fluorescent supramolecular polymer metallogel based on Al3+ coordinated cross-linking of quinoline functionalized- pillar[5]arene act as multi-stimuli-responsive materials

A novel supramolecular polymer metallogel ( QP5-AlG ) has been constructed by cross-linking of bis-8-hydroxyquinoline functionalized pillar[5]arene with Al³⁺. The metallogel QP5-AlG shows light blue aggregation induced emission (AIE) in DMSO/H₂O binary solution. Interestingly, the QP5-AlG shown multiple external stimuli-responsive behaviors such as temperature, guest compounds, acid, base and so on. The QP5-AlG can be used as a fluorescent material for detection of Fe³⁺, F^-, trifluoroacetic acid (TFA) and triethylamine (TEA) by different fluorescence states (“on” or “off”). The (limits of lowest detection) LOQs of the QP5-AlG for Fe³⁺, F^-, TFA and TEA are in the range of 4.39 × 10^-9-1.82 × 10^-7 M. More interestingly, a QP5-AlG -based rewritable and erasable fluorescent platform was demonstrated, which offers a potential testbed for performing “write-erase-write” cycles multiple times. This study provides insight into the development of novel multifunctional supramolecular materials.     

trans—和cis—(η~5—C_5Me_5)2Mo_2(μ_2—S)_2(t—O)_2[Me=CH_3—]的合成和结构

trans—(η~5—C_5Me_5)_2Mo_2(μ_2—S)_2(t—O)_2[Ⅰ]和cis—(η~5—C_5Me_5)Mo_2(μ_2—O)_2(t—O)_2(Ⅱ]是由Mo(CO)_6和C_5(CH_3)_5H的反应产物(η~5—C_5Me_5)_2Mo_2(CO)_4与(CH_2)_3S反应中同时得到的。晶体[Ⅰ]属四方晶系,空间群为P4_2/n,单胞参数;a=b=16.317,c=8.463,V=2253.16,Z=4。晶体[Ⅱ]亦属四方晶系,空间群为P42_1c,单胞参数:a=b=12.101,c=15.425,V=2258.54,Z=4 [Ⅰ]和[Ⅱ]分子分别具有C_1—T和C_2—2对称性。如把C_5Me_5-看成具有理想的园柱体对称性,则它们分别具有C_(2h)—2/m和C_(2v)—mm2对称性。在[Ⅰ]中Mo_2(μ_2—S)_2为菱形平面结构,而[Ⅱ]中则畸变成“蝶式”结构。由两个钼原子之间的距离(2.902和2.808)可以看出钼一钼间作用属于单键的范围内。所以它们是具有金属单键的双钼金属簇的两个立体异构体。     

基于认识化学正向价值的教学实践——以“二氧化碳*”为例

模拟大型科普求真类节目《是真的吗？》创设学习氛围;通过基于生活生产实际的“日常灭火可否用N₂代替CO₂”“深海捕获CO₂可否调控温室效应”“石油采矿业中,向油井下注射1吨CO₂可否增产原油3~5吨”“用石灰水可否保鲜鸡蛋”等4个核心问题及3个真假难辨的小问题,引导学生从化学的正向视角深刻认识二氧化碳的性质;利用移动磁贴板设计板书,引导学生经历并建构结构化知识体系。     

Nucleosides. 130. Synthesis of 2′-Deoxy-2′-substituted- and 5′-Deoxy-5′-substituted-ψ-uridine Derivatives. Crystalline and Molecular Structure of 2′-Chloro-2′-deoxy-1,3-dimethyl-ψ-uridine. Studies Directed Toward the Synthesis of 2′-Deoxy-2′-substituted-arabino-Nucleosides. 1

A method was developed to prepare 5′-deoxy-5′-substituted-ψ-uridine derivatives 4 from 3′,5′-O-(1, 1, 3, 3-tetraisopropyldisiloxanyl)-1,3-dimethyl-ψ-uridine 1 via a silyl rearrangement reaction. Nucleophilic displacement of the mesyloxy function of 2′-O-mesyl-1,3-dimethyl-ψ-uridine 7 afforded products with the 2′-substituent in the “down” ribo configuration 8 . X-Ray crystallographic analysis of the 2′-chloro derivative 8a firmly established the molecular structure of 8 and provided evidence for neighboring group participation of the 4-carbonyl function of 7 during the nucleophilic reactions. Treatment of 1,3-dimethyl-ψ-uridine 11 with α-acetoxyisobutyryl chloride afforded a mixture from which two 2′-chloro-2′-deoxy-C-nucleosides were obtained. The major product (33% yield) was identical with 8 . The minor product (7% yield) was consequently assigned the arabino nucleoside 14 . This is the first direct introduction of a 2′-substituent in the “up” configuration in a preformed pyrimidine nucleoside.     

Homocoenzyme B12 and Bishomocoenzyme B12: Covalent Structural Mimics for Homolyzed,Enzyme‐Bound Coenzyme B12

Efficient electrochemical syntheses of “homocoenzyme B₁₂” ( 2 , Co_β‐(5′‐deoxy‐5′‐adenosyl‐methyl)‐cob(III )alamin) and “bishomocoenzyme B₁₂” ( 3 , Co_β‐[2‐(5′‐deoxy‐5′‐adenosyl)‐ethyl]‐cob(III )alamin) are reported here. These syntheses have provided crystalline samples of 2 and 3 in 94 and 77 % yield, respectively. In addition, in‐depth investigations of the structures of 2 and 3 in solution were carried out and a high‐resolution crystal structure of 2 was obtained. The two homologues of coenzyme B₁₂ ( 2 and 3 ) are suggested to function as covalent structural mimics of the hypothetical enzyme‐bound “activated” (that is, “stretched” or even homolytically cleaved) states of the B₁₂ cofactor. From crude molecular models, the crucial distances from the corrin‐bound cobalt center to the C5′ atom of the (homo)adenosine moieties in 2 and 3 were estimated to be about 3.0 and 4.4 Å, respectively. These values are roughly the same as those found in the two “activated” forms of coenzyme B₁₂ in the crystal structure of glutamate mutase. Indeed, in the crystal structure of 2 , the cobalt center was observed to be at a distance of 2.99 Å from the C5′ atom of the homoadenosine moiety and the latter was found to be present in the unusual syn conformation. In solution, the organometallic moieties of 2 and 3 were shown to be rather flexible and to be considerably more dynamic than the equivalent group in coenzyme B₁₂. The homoadenosine moiety of 2 was indicated to occur in both the syn and the anti conformations.     

Equilibrium structure and harmonic force field of the known PH3 and the unknown PH5

The equilibrium geometries and harmonic force fields of PH₃ and PH₅ are calculated in an ab initio way including electron correlation. The results for PH₃ are in very good agreement with experimental values, whereas those for PH₅ have to be regarded as predictions. We find for PH₅ in its equilibrium D _3h structure r _ax = 1.47 Å, r _eq = 1.42 Å and the harmonic vibration frequencies in Table 7 given under the heading “CEPA”. The barrier for Berry inversion is 2 kcal/mol. The ab initio calculation of phosphoranes such as PH₅ not only requires the inclusion of polarization functions (d on P and p on H) but is also very sensitive to the choice of these polarization functions. This problem is taken care of by a detailed comparison of various basis sets. It is confirmed that a (10/6) basis for P in “double zeta contraction” is better balanced than a (12/9) basis in “double zeta contraction” and that the total energy is not a good criterion for the quality of a basis.     

On triazoles. VIII The reaction of 5-amino-1,2,4-triazoles with ethyl 2-cyano-3-ethoxyacrylate and 2-cyano-3-ethoxyacrylonitrile

The reaction of different 5-amino-3-Q-1H-1,2,4-triazoles 1 with ethyl 2-cyano-3-ethoxyacrylate ( 5a ) and 2-cyano-3-ethoxyacrylonitrile ( 5b ) to yield either the a type 5-amino-, or the b type 7-amino-1,2,4-triazolo[1,5-a]-pyrimidine derivatives 6–10 was studied. The structure of compounds 6 and 9 was proved by their degradation to the corresponding derivatives 17a and 18a , respectively, through intermediates 11a, 12a, 13a, 14a, 15a and 16a , respectively. The structure of derivatives 7, 8 and 10 was proved on the basis of the analogy of their uv spectra with those of 6a and 9a , respectively. The isolation of the intermediates 19 and 20 helped to prove the mechanism of the reactions leading to the formation of 6a and 9a , respectively. In the reaction of the N-substituted 5-amino-1,2,4-triazoles with 5a the expected condensed ring products were not formed. Instead the aminoacrylates 22 and 24 were obtained. The “Z”-“E” isomeric structure of derivatives 19, 20, 22 and 24 was proved with the help of their pmr spectra. The “Z” isomeric structure of the thermodynamically stabile 22 was corroborated with the help of its proton coupled cmr spectra, too.     

Crystallization and ordering of complex oxide structures. I. “Splat-cooled” Nb2O5TiO2

“Splat-cooled” Nb₂O₅TiO₂ with a melt composition corresponding to TiNb₃₈O₉₇ has been examined by high-resolution electron microscopy and electron diffraction. Previous X-ray work showed this material to be crystalline, despite a cooling rate of about 10⁵ °C sec^?1. The present study reveals a variety of structures ranging from highly ordered block structures to severely disordered regions of uncertain structure and composition. “Double layer” structures are identified, and subtle contrast variations in their crystals are explained in terms of single jogs of overlap structures. Crystallization processes are discussed in the light of these results.     

Ca5Sn2As6, das erste Inoarsenidostannat(IV)

Ca₅Sn₂As₆, The First Inoarsenidostannate(IV) The new compound Ca₅Sn₂As₆ crystallizes in the orthorhombic system (space group Pbam (No. 55)) with the lattice constants s. ?Inhaltsübersicht”?. In the structure SnAs₄-tetrahedra are connected by common corners to ?Einereinfach”? chains. The compound belongs to the “Zintlphases”.     

Die Kristallstruktur von Stickstofftrijodid-1-Pyridin NJ3 · C5H5N

The Crystal Structure of Nitrogen Triiodide-1-Pyridine NI₃ · C₅H₅N The crystal structure of NI₃ · C₅H₅N like “Nitrogen Triiodide” NI₃ · NH₃ contains NI₄ tetrahedra as essential structure elements. The tetrahedra are connected by common corners, forming indefinite chains. The pyridine molecule is bonded by its lone electron pair to one of the two iodine atoms that do not participate in the connection of the tetrahedra. Different from NI₃ · NH₃ there are very weak intermolecular interactions between iodine atoms of neighbouring chains.     

Free radical addition of trichloromethyl to caffeine access to C-8 polyhalogenoalkane derivatives and to unexpected 5-trichloromethyl-1,3,7 trimethyl-5,7-dihydrouric acid

The “Electrophilic” trichloromethyl radical was introduced directly into the model purine compound, caffeine, leading to products 2 and 3 (the former being smoothly converted to the corresponding carboxy ester derivative) and to the unexpected C-5 substituted title compound 4.     

CO2 and photo-controlled reversible conversion of supramolecular assemblies based on water soluble pillar[5]arene and coumarin-containing guest

In this communication,a new supramolecualr amphiphile was successfully constructed based on water soluble pillar[5]arene and a unique guest which contain a CO₂ responsive tertiary amine unit and a UV responsive coumarin group.When guest molecule 1 dispersed in water,it self-assembled into sheet-like structures.Upon bubbling CO₂,1 transformed into 1 H due to the tertiary amine unit was protonated,accompany the nano-sheets transformed into vesicles.Further irradiation of 1 H with 365 nm light for 3 h,the coumarin group reacted with each other to form bola-type amphiphie 2 H.In this case,vesicles collapsed and re-assembled into nano-tubes.However,when addition of WPS into the solution of 1 H,the vesicles transformed into micelles,this is due to the formation of supramolecular amphiphile WP5&1 H.Upon irradiation of WP5&1 H with 365 nm light for 3 h,nano-ribbons observed instead of micelles in the solution.Notably,nanotubes from 2 H could also transform into nano-ribbons after adding WPS.The selfassembly process and the resultant assemblies were characterized by TEM,SEM,DLS,SAXS and NMR technologies.Due to both CO₂ and light are "green" for living organisms,we anticipated our system can offer the possibilities in "on demand" drug absorption and release.