Physical Sciences and Mathematics Commons^™

The Effect Of Variation Of N-Substituents On Oxidopyridinium Ions In (4+3) Cycloadditions, Zahria Patrick, Madison Clark

Undergraduate Research Symposium

The aim of this research project is to expand the scope of 4 + 3 cycloadduct chemistry by varying functional groups attached to the prerequisite oxidopyridinium ion for each respective cycloadduct product. While N-substitution of the pyridinium precursor is known to proceed smoothly if alkylated by a lone methyl group, we evaluated the effect a larger alkyl group would have on the overall yield of the 4 + 3 cycloadduct product.

Isobutyl triflate, generated from the known reaction between isobutyl alcohol and triflic anhydride, was reacted with ethyl 5-hydroxy-nicotinate to generate the respective N-isobutyl oxidopyridinium ion in quantitative …

Etherification Of Propargylic Alcohol Using Ferrocenium Ions, Cody Amann, Sai Anvesh Bezawada, Eike B. Bauer

Undergraduate Research Symposium

Etherification of Propargylic Alcohol using Ferrocenium Ions

Cody Amann, Sai Anvesh Bezawada and Eike B. Bauer*

Department of Chemistry and Biochemistry, University of Missouri-St.Louis, MO 63121

Our research efforts are directed toward the improvement of iron-based catalyst systems. The Bauer research group recently found that the ferrocenium cation is a catalytically active in the etherification of propargylic alcohols. My research was to compare the effect of two different counteranions of the ferrocenium cation on the catalytic activity. Etherification test reactions were performed using 2-methyl-2-phenol-propargylic alcohol and n-butanol to afford the corresponding propargylic ether substitution products. The complexes used …

The Synthesis Of Deuterated Isohumulones For Use As Internal Standards In Lc-Ms Stable Isotope Dilution Assays, Patrick Gleason, Bruce Hamper Dr.

Undergraduate Research Symposium

Humulones are compounds that are prevalent in the hops flowers (Humulus Lupulus) used in beer brewing. These compounds undergo isomerization during the brewing process, and the resulting isohumulones are considered to be the primary contributors to the bitter flavors present in beer. As such, quantifying their presence, and the relative presence of their homologs(n-, co-, ad-), is of great importance in the characterization of beer. In this effort, one of the homologs of humulone (co) was isolated before being subsequently isomerized and deuterated for the purpose of analyzing beer by stable isotope dilution assay mass spectrometry(SIDA-MS). The addition of this …

Identification Of 4-Isopropyl–Thiotropolone As A Novel Anti-Microbial: Regioselective Synthesis, Nmr Characterization, And Biological Evaluation, Mohamed Elagawany, Mohamed Elagawany, Lamees Hegazy, Feng Cao, Maureen Donlin, Nigam Rath, John Tavis, Bahaa Elgendy, Bahaa Elgendy

Chemistry & Biochemistry Faculty Works

We have synthesized and separated tosylated thujaplicin isomers for the first time, and elucidated their structures using 1D, 2D-NMR techniques and X-ray crystallography. The tosylated isomers were used to synthesize 4-isopropyl–thiotropolone and 6-isopropyl–thiotropolone in a regioselective manner. 1H and 13C Chemical shifts of synthesized isomers were fully assigned using several NMR experiments, and their isotropic magnetic shielding was calculated using the GIAO (Gauge Including Atomic Orbitals) method and the B3LYP def2-TZVPP level of theory. The calculated chemical shift values were in a good agreement with the experimental results. The biological activity of all synthesized compounds was evaluated against the fungal …

Conformationally Superarmed S-Ethyl Glycosyl Donors As Effective Building Blocks For Chemoselective Oligosaccharide Synthesis In One Pot, Mithila Bandara, Jagodige Yasomanee, Nigam Rath, Christian Pedersen, Mikael Bols, Alexei Demchenko

Chemistry & Biochemistry Faculty Works

A new series of superarmed glycosyl donors has been investigated. It was demonstrated that the S-ethyl leaving group allows for high reactivity, which is much higher than that of equally equipped S-phenyl glycosyl donors that were previously investigated by our groups. The superarmed S-ethyl glycosyl donors equipped with a 2-O-benzoyl group gave complete β-stereoselectivity. Utility of the new glycosyl donors has been demonstrated in a one-pot one-addition oligosaccharide synthesis with all of the reaction components present from the beginning.

A Simplified Direct Lipid Mixing Lipoplex Preparation: Comparison Of Liposomal-, Dimethylsulfoxide-, And Ethanol-Based Methods, Joseph Meisel, George Gokel

Chemistry & Biochemistry Faculty Works

Established transfection methodology often uses commercial reagents, which must be formed into liposomes in a sequence of about half a dozen steps. The simplified method reported here is a direct lipid mixing approach that requires fewer steps, less manipulation, and is less time-consuming. Results are comparable to those obtained with more commonly used methods, as judged by a variety of analytical techniques and by comparisons of transfection results. The method reported here may be applied to non-liposome-forming compounds, thereby greatly expanding the range of structures that can be tested for transfection ability.

Uplc–Qtof–Ms And Nmr Analyses Of Graviola (Annona Muricata) Leaves, Ingrid De Moraes, Paulo Ribeiro, Flávio Schmidt, Kirley Canuto, Guilherme Zocolo, Edy De Brito, Rensheng Luo, Kristy Richards, Kevin Tran, Robert Smith

Chemistry & Biochemistry Faculty Works

No abstract provided.

Stereocontrolled 1,2-Cis Glycosylation As The Driving Force Of Progress In Synthetic Carbohydrate Chemistry, Swati Nigudkar, Alexei Demchenko

Chemistry & Biochemistry Faculty Works

Recent developments in stereoselective 1,2-cis glycosylation that have emerged during the past decade are surveyed herein. For detailed coverage of the previous achievements in the field the reader is referred to our earlier reviews: A. V. Demchenko, Curr. Org. Chem., 2003, 7, 35–79 and Synlett, 2003, 1225–1240.

Relay Cross Metathesis Reactions Of Vinylphosphonates, Raj Malla, Jeremy Ridenour, Christopher Spilling

Chemistry & Biochemistry Faculty Works

Dimethyl (β-substituted) vinylphosphonates do not readily undergo cross metathesis reactions with Grubbs catalyst and terminal alkenes. However, the corresponding mono- or diallyl vinylphosphonate esters undergo facile cross metathesis reactions. The improved reactivity is attributed to a relay step in the cross metathesis reaction mechanism.

New Bis(Imino)Pyridine Complexes Of Iron(Ii) And Iron(Iii), And Their Catalytic­ Activity In The Mukaiyama Aldol Reaction, Pushkar Shejwalkar, Nigam Rath, Eike Bauer

Chemistry & Biochemistry Faculty Works

New iron(II) and iron(III) complexes bearing bis(imino)pyridine ligands were synthesized and successfully applied to the Mukaiyama aldol reaction. The two complexes [FeCl2 L] (L = bis(imino)pyridine ligand, 55% isolated yield) and [LFe(μCl)3FeCl3] (76%) were obtained employing FeCl2 and FeCl3 iron sources, respectively, and characterized by elemental analyses, mass spectrometry, IR spectroscopy and, one example, by X-ray diffraction. The two new iron complexes were subsequently employed as catalysts in the Mukaiyama aldol reaction after abstraction of two chlorides by AgSbF6 to obtain the aldol products in 43% to virtually quantitative yield (CH2Cl2 solvent, room temperature, 3.5 to 16 h reaction time). …

2-Allylphenyl Glycosides As Complementary Building Blocks For Oligosaccharide And Glycoconjugate Synthesis, Hemali Premathilake, Alexei Demchenko

Chemistry & Biochemistry Faculty Works

The O-allylphenyl (AP) anomeric moiety was investigated as a new leaving group that can be activated for chemical glycosylation under a variety of conditions, through both direct and remote pathways. Differentiation between the two activation pathways was achieved in a mechanistic study. The orthogonal-type activation of the AP moiety along with common thioglycosides allows for the execution of efficient oligosaccharide assembly.

Effect Of A Strategically Positioned Methoxy Substituent On The Photochemistry Of 3-Aryl-3h-1-Oxacyclopenta[L]Phenanthren-2-Ones, Roshini Thumpakara, Binoy Jose, Perupparampil Unnikrishnan, Sreedharan Prathapan, Nigam Rath

Chemistry & Biochemistry Faculty Works

Irradiation of 3-methoxy-3-aryl-3H-1-oxacyclopenta[l]phenanthren-2-one derivatives 5a–d resulted in singlet-mediated decarbonylation reaction leading to the formation of phenanthrene derivatives 9a–d. The structure of the photoproduct was unequivocally established on the basis of X-ray crystallographic analysis.

(1e,3e)-1,4-Bis(4-Methoxyphenyl)Buta1,3-Diene, Gopinathan Narayan, Nigam Rath, Suresh Das

Chemistry & Biochemistry Faculty Works

The title compound, C18H18O2, which exhibits blue emission in the solid state, is an inter­mediate in the preparation of liquid crystals and polymers. The mol­ecule is located on an inversion centre. In the crystal, mol­ecules are arranged in a herringbone motif.

2,4,6-Triphenyl­Aniline, Onome Ugono, Stephanie Cowin, Alicia Beatty

Chemistry & Biochemistry Faculty Works

Individual mol­ecules of the title compound, C24H19N, do not participate in hydrogen-bonding inter­actions due to the steric bulk of the phenyl rings ortho to the amine. The dihedral angles between the central ring and the pendant rings are 68.26 (10), 55.28 (10) and 30.61 (11)°.

New Chiral Phosphoramidite Complexes Of Iron As Catalytic Precursors In The Oxidation Of Activated Methylene Groups, Pushkar Shejwalkar, Nigam Rath, Eike Bauer

Chemistry & Biochemistry Faculty Works

New phosphoramidite complexes of iron were synthesized and structurally characterized. Reaction of the known chiral phosphoramidites (RO)2PNR’2 (R = binaphthyl, R’ = CH3, 1a; R = binaphthyl, R’ = benzyl, 1b) with [FeBr(Cp)(CO)2] afforded the title compounds [FeBr(Cp)(CO)(1a,b)] (4a,b) in 34 and 65 % isolated yields as mixtures of diastereomers, since both the metal and the ligand are stereogenic. Similarly, reaction of 1b with [Fe(Cp)I(CO)2] in the presence of catalytic [Fe(Cp)(CO)2]2 afforded [Fe(Cp)I(CO)(1b)] (5b) in 81% yield as a mixture of diastereomers. The molecular structures of 4a, 4b and 5 were determined, revealing a pseudo octahedral coordination geometry about the …

Critically Evaluated Thermochemical Properties Of Polycyclic Aromatic Hydrocarbons, María Roux, Manuel Temprado, James Chickos, Yatsuhisa Nagano

Chemistry & Biochemistry Faculty Works

No abstract provided.

Modeling The Physical Properties Of A Homologous Series On The Melting Temperatures And Densities Of N-Alkanes And Their Simple Alkyl-Derivatives, Antun Rubčić, Jasna Rubčić, James Chickos

Chemistry & Biochemistry Faculty Works

No abstract provided.

2-Phenyl-3-(5,6,7,7a-Tetrahydro-1h,3h-Pyrrolo[1,2-C]Oxazol-3-Ylidene)-1-Propene-1,1-Dicarbonitrile And 4-(4-Methoxyphenyl)-2,6-Bis(Methylthio)Pyridine-3-Carbonitrile, M. George, S. Das, C.V. Ashokan, N.P. Rath, M.V. George

Chemistry & Biochemistry Faculty Works

The reaction of 3-aryl-2-cyano-5,5-bis(methylthio)penta-2,4-dienenitrile, (1), with (L)-(-)-2-hydroxymethylpyrrolidine, (2), gave two types of product, the normal substitution product, (3), and a pyridine derivative, (4). The structures of two representative examples, 2-phenyl-3-(5,6,7,7a-tetrahydro1H,3H-pyrrolo[1,2-c]oxazol-3-ylidene)-1-propene-1,1-dicarbonitrile, (3a), as its hemibenzene solvate, C17H14N3O.0.5C6H6, and 4-(4-methoxyphenyl)-2,6-bis(methylthio)pyridine-3-carbonitrile, (4b), C15H14N2OS2, have been unambiguously established by X-ray crystallographic analysis. The molecular packing of (4b) involves loosly held dimers with S1...S1' distances of 3.424 (1) Å.