基于聚丙交酯的光固化型可生物降解聚氨酯丙烯酸酯的合成和表征

基于聚醚酯的聚氨酯丙烯酸酯具有应用于组织工程支架材料及相关生物医用材料的潜力,研究其可生物降解性及影响因素非常重要.聚醚酯是由PEG(Mw=400)引发L-丙交酯开环聚合而得到的PLLA-PEGPLLA(PLEL)嵌段共聚物.它与二异氰酸酯(异佛尔酮二异氰酸酯和六亚甲基二异氰酸酯)反应,并用甲基丙烯酸羟乙酯封端,得到聚氨酯丙烯酸酯低聚物,然后通过紫外固化得到聚氨酯丙烯酸酯材料(PUA).用NMR和GPC对PLEL二醇和预聚物进行了组成和分子量表征,用DSC和DMA对PUA进行了结构和物理性能表征以及用接触角、吸水率和质量分析方法对材料的亲水性和降解性能进行了表征.结果发现,随着PLLA疏水链段变长,PLEL软段分子量增大,材料的亲水性降低,交联度和降解速率变小.相同的软段,基于硬段HDIHEMA的PUA材料比IPDI-HEMA的PUA有较低的T_g,较高的亲水性和降解速率.因为IPDI有环状结构,降低了PUA与水的相互作用.在3种不同降解条件下,氧化降解速率最高,酶解的速率高于水解.PUA材料的氧化降解速率取决于软段中PEG的含量,PLEL1000-HDI中PEG含量最高,其氧化降解最快,13周内失重率达到82.6%.     

Visible light mediated metal-free oxidative aromatization of 1,3,5-trisubstituted pyrazolines

The visible light mediated oxidation of 1,3,5-trisubstituted pyrazolines under metal-free conditions was developed. Various substituted pyrazolines were oxidized to pyrazoles by irradiation with visible light/sunlight. A plausible mechanism was proposed for the light mediated oxidation proceeding via formation of intermediates with electron rich C-3 positions and electron deficient C-5 positions. Correlation between the electronic effect induced by the aryl substituents and the rate of oxidation was studied by UV–vis spectroscopy. This correlation study supported the proposed mechanism. Electron withdrawing substituents at the 3-phenyl group and electron releasing substituents at the 5-phenyl group enhanced the rate of oxidation; whereas, electron donating substituents at the 3-phenyl group and electron withdrawing substituents at the 5-phenyl group reduced the rate.     

Removal of single and dual ring thiophene’s from dodecane using cavitation based processes

Utilising cavitation for enhancing oxidative desulphurization has been investigated for nearly-two decades with recent investigations shifting focus from low-capacity acoustic cavitation (AC) to scalable hydrodynamic cavitation (HC). This work focuses on developing a viable means for removing thiophene’s from fuels. In the first phase of this work, use of vortex based HC devices for removal of single and dual ring thiophenes from dodecane was investigated. HC was shown to be able to remove single ring thiophene from dodecane without using any external catalyst or additives. However, in absence of catalyst or additives, it was not possible to remove dual ring thiophenes such as dibenzothiophene using HC. Therefore, in the second phase of this work, various strategies based on use of catalyst or additives to augment cavitation based process were investigated. AC based experiments were opted for shortlisting suitable catalysts and additives for intensifying cavitation based processes. The influence of using oxidant (H₂O₂) and carboxylic acid catalysts on efficacy of removal of dual ring thiophenes is presented. Several conditions were tested, and the optimal volumetric ratios of 0.95 v/v % H₂O₂ and 6.25 v/v % HCOOH was identified and utilised throughout the remainder of the study. Regeneration of extractant which accumulates oxidised sulphur species from dodecane was also investigated using AC. The additives and process conditions reported in this work are useful for enhancing desulphurization performance.     

Unveiling the relevance of the redox character of nitroaromatic and nitroheteroaromatic compounds as potential medicines

This review discusses the state of the art, challenges, and perspectives in recent applications of nitroaromatics and nitroheteroaromatics, which are redox-bio-activated drugs or leads, in Medicinal Chemistry. It deals mainly with the electrochemical approach toward the electron transfer-based molecular mechanisms of drug action, drug design, estimation and measurement of redox potentials, correlation of physicochemical and pharmacological data, and electrochemical studies of the main representatives of nitro-containing prodrugs, along with approaches to combat their toxicity issues, aiming at a better therapeutic profile. Electrochemical investigation plays essential roles, being strategic in the design and discovery of potential medicines.     

Facile amidation of esters with aromatic amines promoted by lanthanide tris (amide) complexes

The development of catalysts capable of catalyzing amidation of esters with amines to construct amides under mild conditions is of great importance. Compared to aliphatic amines, the direct catalytic amidation of esters with less nucleophilic aromatic amines is rather difficult. Employing simple lanthanide tris (amide) complexes Ln[N (SiMe₃)₂]₃(μ-Cl)Li (THF)₃ as the catalysts, it was found a broad range of aromatic amines and esters were efficiently converted into various amides in good yields under mild conditions. A plausible mechanism for this transformation was experimentally supported as starting from an amide exchange reaction between the lanthanide tris (amide) complex and the substrate amine.     

Efficient synthesis of the C/D rings of atisine-type C20-diterpenoid alkaloids

A bicyclo[2.2.2]octane C/D ring system,with a lactonic ring at C-8 and C-9,of the atisine-type C₂₀-diterpenoid alkaloids,was successfully synthesized,using an oxidative dearomatization/intramolecular Diels-Alder reaction.     

Synthesis,structure and properties of N-aminosaccharin – A selective inhibitor of human carbonic anhydrase I

Previously unknown N-aminosaccharin was prepared in good yield via the one-step direct amination of saccharin sodium salt with hydroxylamine-O-mesitylenesulfonic acid (MSH) and its reactivity investigated. N-aminosaccharin and its derivatives were tested against hCA isoforms and the parent compound was identified to be a selective, low micromolar inhibitor (K_i = 8.8 μM) of hCA I. These findings provide a ligand-efficient starting point for the design of potent hCA I inhibitors – a promising drug target for retinal/cerebral edema treatment.     

Effect of Amines on the Selective Bromination of Some β-Substituted-2-Butenoic Esters

The effect of amines on the selective bromination of some β-substituted-2-butenoic esters is described. The bromination of methyl (Z)-4-t-butyldiphenylsilyloxy-3-methylbutenoate 2 in the presence of DIPEA (N, N-diisopropylethylamine) and the successive treatment of the obtained dibromide with potassium t-butoxide afford the desired Z bromide selectively. But the corresponding E bromide forms exclusively when 2, 6-di-t-butyl-4-methylpyridine is used in the bromination.