2,2-亚戊基-1,3-二氧六环-4,6-二酮与原甲酸三乙酯和芳香胺的反应

剂,在有机合成中已有一定应用。开展Meldrum's 酸系列化合物的研究,旨在:1.寻找有结构特点的新试剂,2.合成一系列新化合物,3.研究新化合物的应用。本文通过控制反应温度(28～29℃)催化剂用量(比文献用量多近一倍),提高了2,2-亚戊基-1,3-二氧六环-4,6-二酮(PDDO,3)的制备得率(由15%     

香豆素类化合物的一种新合成方法

香豆素类化合物是一类重要的有生物活性的天然产物,也可用作香料、阻凝剂和三线态光敏剂。用 Meldrum 酸合成该类化合物,已有一些报道。我们在研究 Meldrum 酸系列     

Total synthesis and determination of the absolute configuration of frondosin B.

Two concise syntheses of (+/-)-frondosin B (1), an interleukin-8 receptor antagonist, have been achieved from commercially available 5-methoxysalicylaldehyde. The seven-membered ring in ketone 33, the common intermediate for both syntheses, was built by a classical Friedel-Crafts reaction. The key step of the first route was facile cationic cyclization of the vinylogous benzofuran to the trisubstituted olefin (30 --> 16 + 38) to construct a six-membered carbocycle. Although this route demonstrated the efficacy of the stepwise approach to the frondosin ring-system, it also resulted in olefinic isomers that were easily isomerized in acidic conditions. In the second route, we utilized a Diels-Alder reaction between sterically demanding diene 42 and nitroethylene to fix the double bond in its required position in the resultant dimethylcyclohexane ring. A third total synthesis was devised for the purpose of determining the absolute configuration of frondosin B. It reached diene 42, this time in the enantiomerically defined form. From this point, naturally configured frondosin B was obtained in the enantiomerically enriched form. These studies establish the absolute configuration of the secondary methyl center in frondosin B to be R.     

High‐Throughput Screening of Mechanical Properties on Temperature‐Gradient Polyurethaneurea Libraries

Combinatorial libraries of segmented polyurethaneurea with gradients in curing temperature were prepared and characterized using a novel high‐throughput mechanical instrument. Stress/strain profiles were taken at different temperature positions on the libraries, and a structure/property relationship between microstructure and mechanical properties was established by correlating the measured strength and strain at break to high‐throughput AFM and FT‐IR measurements on the same library. These results demonstrate the feasibility of rapid and accurate screening of mechanical properties, and their correlation to structure, by using gradient combinatorial polymer libraries.

Impact energy/thickness and elongation at break versus cure T for a T‐gradient SPUU library.     

Silver(I) 3-aminomethylpyridine complexes, part 2: effect of ligand ratio, hydrogen bonding, and pi-stacking with an interacting anion

Reaction of 3-aminomethylpyridine (3-amp) with silver(I) salts of triflate (OTf-) and trifluoroacetate (tfa-) produce a variety of multidimensional coordination networks whose structures depend on the stoichiometry of the components present. A 1:1 ratio of 3-amp to AgX produces a linear polymer, 1, when X = tfa- and a planar sheet, 2, when X = OTf-. Addition of a second equivalent of ligand increases the dimensionality of both structures by one to form a two-dimensional sheet, 3, and a three-dimensional system, 4, for their respective anions. Addition of 2,2'-bipyridine (bipy) to solutions of any of the previous compounds produces the fixed-ratio complexes 5 (tfa- salt) and 6 (OTf- salt). The bipyridyl ligand halts the polymerization of compounds 1-4 by cutting the chain after each silver(I) link and forcing a 1:2:2 ratio of 3-amp to AgX to bipy. Compound 5, however, remains polymeric in nature due to the closed-shell Ag-Ag interactions of the planar metals holding the monomers together. Differences between structures of each ratio stem from the differences in basicity and in the extra degree of H-bonding ability that the OTf- anion has over tfa-.     

Synthesis and Biological Activities of Azalamellarins

The synthesis of azalamellarins, a new series of lactam analogues of biologically active lamellarins, was achieved using Cu^I‐mediated and microwave‐assisted C? N_amide bond formation. Seventeen azalamellarins, including N‐allylazalamellarins and N‐propylazalamellarins χ‐D, L ‐N, and J‐dehydro J, were synthesized and evaluated for their cytotoxicity against the cancer cell lines HuCCA‐1, A‐549, HepG2, and MOLT‐3. The results showed that certain azalamellarins exhibited good activities in the micromolar IC₅₀ value range (IC₅₀=the drug concentration that causes 50 % of cell‐growth inhibition after 72 h of continuous exposure to the test molecule), comparable to their parent lamellarin analogue.     

Accelerated solvent extraction of fluometuron from selected soils

Accelerated solvent extraction (ASE) is a recently developed extraction technique that is more rapid and produces less waste than do conventional liquid/liquid extraction methods. Optimal conditions were determined for ASE of fluometuron from 2 Weswood clay loam soils. Two solvents (acetonitrile and methanol), 2 temperatures (50 and 100 degrees C), and the number of static cycles (1, 2, and 3) were evaluated. The most efficient and reproducible extractions were obtained when methanol was combined with a 50 degrees C extraction temperature and the static cycle was repeated 3 times. These experiments indicated that existing extraction methods for fluometuron can easily be adapted for ASE.     

固相微萃取与高效液相色谱联用技术的进展

 较全面地评述了固相微萃取与高效液相色谱联用技术的发展与应用 ,包括该技术的原理、接口装置、涂层材料等。     

A general,enantioselective synthesis of 2-substituted thiomorpholines and thiomorpholine 1,1-dioxides

In the course of our drug discovery programs, we had need to access chiral, 2-substituted thiomorpholines and their oxidized congeners, thiomorpholine 1,1-dioxides. Here, we disclose a high-yielding, general protocol for the enantioselective synthesis of C2-functionalized thiomorpholines and thiomorpholine 1,1-dioxides.     

Enhancing aperiodic stochastic resonance through noise modulation

We show that the conventional stochastic resonance (SR) effect for aperiodic signals in a model neuron can be enhanced by modulating the intensity of the input noise (which could be introduced artificially in bioengineering applications) with either the input signal or the unit's output rate signal. We analyze SR enhancement theoretically and numerically. We discuss how this work provides the theoretical foundation for the development of an optimal noise-based technique for enhancing sensory function. (c) 1998 American Institute of Physics.