Rearrangement of a mesylate tropane intermediate in nucleophilic substitution reactions. Synthesis of aza-bicyclo[3.2.1]octane and aza-bicyclo[3.2.2]nonane ethers,imides, and amines

Nucleophilic substitution of 2beta-mesyloxymethyl-N-methyl-3beta-p-tolyl-tropane intermediate with alkoxides, metal imides, or amines was found to lead not only to the expected bicyclo[3.2.1]octane (tropane) ether, imide, and amine derivatives but also to unexpected bicyclo[3.2.2]nonane derivatives. When alkoxides were used as nucleophile, only the rearranged bicyclo[3.2.2]nonane structure was obtained, whereas the use of amines or imides as nucleophile afforded a mixture of the two structures. The bicyclo[3.2.2]nonane structure was assigned by NMR analysis.     

Acryloyl-modified cellulose nanocrystals: effects of substitution on crystallinity and copolymerization with acrylic monomers

Cellulose nanocrystals (CNCs) are crystalline nano-rods that have high specific strength with hydroxyl surface chemistry. A wide range of chemical modifications have been performed on the surface of CNCs to increase their potential to be used in applications where compatibilization with other materials is required. Understanding the surface chemistry of CNCs and critically examining the functionalization technique are crucial to enable control over the extent of modification and the properties of CNCs. This work aims to optimize the surface modification of wood-derived CNCs with isocyanatoethyl methacrylate (IEM), a bifunctional molecule carrying both isocyanate and vinyl functional groups. We studied the effect of modification reaction time and temperature on the degree of substitution, crystallinity, and morphology of the CNCs. We found that the degree of modification is a strong and increasing function of reaction temperature over the range studied. However, the highest temperature (65 °C) and the longest time of reaction (6 h) resulted in shorter, thinner, and less crystalline CNCs. We obtained surface hydroxyl conversion of 60.1?±?6% and percent crystallinity of 84% by keeping the reaction shorter (30 min) at 65 ºC. Also, the copolymerization ability of modified CNCs was verified by polymerizing attached IEM groups with acrylic monomers via solution polymerization. The polymer-grafted CNCs (6% w/w) dispersed better in an acrylic polymer matrix compared to unmodified CNCs (umCNCs), resulting in approximately 100% improvement in the tensile strength and about 53% enhancement in the hardness of the acrylic, whereas addition of 6% w/w umCNCs did not influence the strength and hardness.

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Investigation of carbon dioxide modified supercritical and near supercritical carrier streams for flow injection systems

Since flow injection (FI) is a dilution technique, efforts have been undertaken to minimize online dilution or dispersion. Solutes in supercritical fluids exhibit increased diffusion coefficients which have been shown to decrease dispersion of the sample zone. This work investigates the use of supercritical fluids (or CO₂ modified fluids) as carrier streams for FI. Both a non-reacting tracer and an online chemical reaction were employed to investigate the behavior of solutes in supercritical and near critical systems. Further, these results are compared to those obtained in the system studied with a conventional carrier stream. Plots of peak response vs% CO₂ modifier increase with a sharp break at moderate modifier composition (20–30%). Plots of peak variance vs% CO₂ modifier show decreased variance with increasing % modifier. The system was also optimized with regards to temperature and pressure. The optimized system displayed improved limits of detection and decreased variance relative to 0% CO₂ modifier carrier streams.     

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.     

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.     

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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.     

Effect of Poly(3‐octylthiophene) Doping on the Attachment and Proliferation of Osteoblasts

The effect of doping P3OT with ferric chloride on the attachment and proliferation of MC3T3‐E1 osteoblasts is reported. Cell density and area correlated strongly with doping concentration: cells were larger and exhibited better spreading as doping increased. Cells cultured on undoped P3OT showed a decrease in proliferation between 24 and 48 h followed by a recovery after 72 h. However, this trend diminished with increasing doping concentration, and disappeared completely at the highest dopant level investigated. Analysis of cell‐cell spatial distributions suggested that contact inhibition of proliferation occurred similarly on both undoped and doped P3OT. From these results, FeCl₃‐doping had no significant deleterious effect on attachment or proliferation of osteoblasts in vitro.