Angela Winstead

Microwave synthesis of quaternary ammonium salts.

The microwave synthesis of several quaternary ammonium salts is described. The synthesis provides comparable or better yields than published methods with reduced reaction times and in the absence of solvent.

Synthesis of Quaternary Heterocyclic Salts

The microwave synthesis of twenty quaternary ammonium salts is described. The syntheses feature comparable yields to conventional synthetic methods reported in the current literature with reduced reaction times and the absence of solvent or minimal solvent.

Microwave synthesis of cyanine dyes.

Abstract Heptamethine cyanine dyes are a class of near infrared (NIR) dyes that have captured the interest of the scientific community. Although applications that utilize NIR fluorescence technology are rapidly expanding, progress is limited by the lack of availability and cost of suitable compounds that can be utilized as labels and/or probes. Herein, we report the use of microwave assisted organic synthesis of five NIR cyanine dyes in yields ranging from 64–83% with a significant reduction in solvent use. Spectra characteristics including absorbance and emission spectra, molar absorptivity, quantum yield, fluorescence lifetime, and redox potentials were determined for each synthesized NIR cyanine dye.

Microwave Synthesis of Near Infrared Heptamethine Cyanine Dye

Cyanine dyes are an interesting class of near infrared (NIR) dyes that have captured the interest of the scientific community. The NIR cyanine dye of interest, heptamethine cyanine dye NIR-1, exhibits characteristics that satisfy the qualifications as an acceptor in a Fluorescence Resonance Energy Transfer (FRET) biosensor [Wher, 1976]. Applications of FRET systems include structure determination and conformation of proteins [Hammer et al., 2002], receptor/ligand interactions [Hammer et al., 2002], and the cellular exposure to environmental toxins [Schwartz and Ulfelder, 1992]. This research stems from an interdepartmental collaboration to develop a NIR FRET biosensor, with significant advantages over the existing systems. A critical component of this endeavor is the development of an efficient environmentally conscious synthesis of novel NIR cyanine dyes utilizing microwave technology. Herein, we report the microwave synthesis of NIR-1. 2,3,3-Trimethyl-1-ethyl-3H-indolium iodide (I) synthesis is advantageous over the reported synthesis due to the significantly reduced reaction time of450 s from 15 h and a decrease in the amount of iodoethane from 5 eq. to 3 eq. The condensation of heterocyclic salt I and bisaldehyde II has been accomplished in 220 s in 85% yield in the microwave oven; benzene has been eliminated from the condensation reaction procedure. Spectral characteristics of NIR-1 were determined and compared to commercially available NIR-1. A significant absence of asymmetry at the broad peak associated with the maximum absorbance wavelength, a slight increase in quantum yield (+—.02) and the blue shift of the maximum absorbance wavelength (—5 nm) was observed.

Application of Microwave Assisted Organic Synthesis to the Development of Near-IR Cyanine Dye Probes

Cyanine dyes are a class of fluorescent organic dyes that have been used extensively as the probe component of chemical and biological sensors. Generally, they are comprised of two nitrogen-containing heterocycles, one of which is positively charged. The heterocycles are linked by a conjugated polymethine chain with an odd number of carbons, common chain lengths are tri (n=1), penta (n=2) and heptamethine (n=3).

1-(5-Carboxy­pent­yl)-2,3,3-trimethyl-3H-indol-1-ium bromide monohydrate

In the title compound, C17H24NO2 +·Br−·H2O, the pentyl group chain in the cation extends nearly perpendicular [N—C—C—C = −64.4 (3)°] to the mean plane of the indole ring with the carboxyl end group twisted such that the dihedral angle between the mean planes of the indole and carboxy groups measures 43.2 (4)°. Both ions in the salt form intermolecular hydrogen bonds (O—H⋯Br and O—H⋯O) with the water molecule. As a result of the Br⋯H—O—H⋯Br interactions, a zigzag chain is formed in the c-axis direction. The crystal packing is influenced by the collective action of the O—H⋯O and O—H⋯Br intermolecular interactions as well as π–π stacking intermolecular interactions between adjacent benzyl rings of the indole group [centroid–centroid distance = 3.721 (13) Å] and intermolecular C—H⋯π interactions between a methyl hydrogen and the benzyl ring of the indole group. The O—H⋯Br interactions form a distorted tetrahedral array about the central Br atom. A MOPAC AM1 calculation provides support to these observations.

The Effects of Synthesized Rhenium Acetylsalicylate Compounds on Human Astrocytoma Cell Lines

Purpose Because of the scarcity of suitable brain cancer drugs, researchers are frantically trying to discover novel and highly potent drugs free of side effects and drug-resistance. Rhenium compounds are known to be nontoxic and exhibit no drug resistance. For that reason, we have developed a series of novel rhenium acetylsalicylato (RAC or ASP) complexes to test their cytotoxicity on brain cancer cells. Also we have attempted to explore the DNAbinding properties of these compounds because many drugs either directly or indirectly bind to DNA. Methods We have treated the RAC series compounds on human astrocytoma brain cancer cell lines and rat normal brain astrocyte cells and determined the efficacy of these complexes through in vitro cytotoxicity assay. We carried out the DNA-binding study through UV titrations of a RAC compound with DNA. Also we attempted to determine the planarity of the polypyridyl ligands of the RAC series compounds using DFT calculations. Results RAC6 is more potent than any other RAC series compounds on HTB-12 human astrocytoma cancer cells as well as on Glioblastoma Multiforme D54 cell lines. In fact, The IC-50 value of RAC6 on HTB-12 cancer cells is approximately 2 μM. As expected, the RAC series compounds were not active on normal cells. The DFT calculations on the RAC series compounds were done and suggest that the polypyridyl ligands in the complexes are planar. The UV-titrations of RAC9 with DNA were carried out. It suggests that RAC9 and possibly all RAC series compounds bind to minor grooves of the DNA. Conclusion Because of the very low activity of RAC6 on normal cells and low lC50 value of on astrocytoma (HTB-12) cell lines, it is possible that RAC6 and its derivatives may potentially find application in the treatment of brain cancers. The DFT calculations and UV titrations suggest that RAC series compounds either bind to DNA intercalatively or minor grooves of the DNA or both. However, it is highly premature to make any definite statement in the absence of other techniques.

Microwave-assisted synthesis of rhodamine derivatives

ABSTRACT The microwave synthesis of 12 rhodamine-derived imines is described. The present work involves condensation of rhodamine hydrazide with various aromatic aldehydes in ethanol under microwave irradiation. The results obtained indicate that, unlike classical heating, microwave irradiation results in higher yields, shorter reaction time, mild reaction condition and simple work-up procedure. The structures of synthesized compounds were confirmed by 1H-NMR, 13C-NMR, FT-IR and high-resolution mass spectra data. GRAPHICAL ABSTRACT

(E)-3′,6′-bis(Diethylamine)-2-[(2-methoxynaphthalen-1-yl)methyleneamino]spiro[isoindoline-1,9′-xanthen]-3-one

The title compound, (E)-3′,6′-bis(diethylamine)-2-[(2-methoxynaphthalen-1-yl)methyleneamino]spiro[isoindoline-1,9′-xanthen]-3-one, was synthesized in 92% isolated yield using microwave-assisted organic synthesis. This new rhodamine derivative was fully characterized by 1H-NMR, 13C-NMR, FTIR and high resolution MS.

1-(6-Ethoxy-6-oxohexyl)-4-methylquinolinium Iodide

The N-ethoxycarbonylhexyl quaternary salt of lepidine has been synthesized in one step in 56% yield. 1H and 13C NMR data are reported.