The roles of silanes as coupling reagents and in deoxygenative alkylations

Silane reagents play important roles in many areas of organic synthesis. This is primarily due to the ability of silanes to bond to more ligands than the traditional four to become hypervalent (i.e. penta- or hexavalent). This hypervalency causes the silicon center to become more Lewis Acidic and causes the formation of carbon nucleophiles from organosilane ligands. These nucleophiles have been used to perform many cross-coupling reactions with organohalide reagents. The research presented in this thesis reports the utility of silane reagents in cross-coupling reactions of Grignard reagents with alkyl halides. This cross coupling was desirable because the silane should act as a mediator, being reformed in the reaction process. Also, similar transformations mediated by metal catalysts suffer from poor reactivity, low yields, and undesired side reactions. Although the results from this study do not show marked improvement over couplings formed in the absence of silane reagents, analysis of the deficiencies of silane-mediated cross-coupling reactions are made as well as proposals for future research. The first indium trichloride catalyzed deoxygenative alkylations of alcohol derivatives using a step-wise reaction plan are reported herein as well as the first study of the possible chiral transfer in the transformation from a C-O bond to a C-C bond via InCl3 mediated alkylative deoxygenation upon the silyl ether derivatives of chiral alcohols. This chiral transfer was believed to take place because of a possible concerted mechanism. Results of this research indicated that chiral transfer does not occur in these types of reactions under the conditions explored due to the formation of a carbocation intermediate in the mechanism. The reactivity observed in the deoxygenative alkylations of a range of alcohols is similar to that of other non-concerted substitution reactions such as preference for 2°, benzylic, and 3° alcohol precursor starting material. Based upon the discoveries made in this line of research, a reasonable mechanism for the InCl3-catalyzed deoxygenative alkylation of alcohol derivatives was found

Sub-Doppler frequency metrology in HD for test of fundamental physics

Weak transitions in the (2,0) overtone band of the HD molecule at $\lambda = 1.38 \, \mu$m were measured in saturated absorption using the technique of noise-immune cavity-enhanced optical heterodyne molecular spectroscopy. Narrow Doppler-free lines were interrogated with a spectroscopy laser locked to a frequency comb laser referenced to an atomic clock to yield transition frequencies [R(1) = $217\,105\,181\,895\,(20)$ kHz; R(2) = $219\,042\,856\,621\,(28)$ kHz; R(3) = $220\,704\,304\,951\,(28)$ kHz] at three orders of magnitude improved accuracy. These benchmark values provide a test of QED in the smallest neutral molecule, and open up an avenue to resolve the proton radius puzzle, as well as constrain putative fifth forces and extra dimensions.Comment: 5 pages, 4 figure

Prenylated p-Hydroxyacetophenone Derivatives from the Giant Senecio johnstonii

The extract of the aerial parts of S. johnstonii afforded five known prenylated p-hydroxyacetophenone derivatives, scopoletin and 5-pentadecyl resorcinol together with the tridecyl derivative. The chemotaxonomic situation is discussed briefly.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28519/1/0000316.pd

Antidiabetic Actions of Endogenous and Exogenous GLP-1 in Type 1 Diabetic Patients With and Without Residual β-Cell Function

OBJECTIVE—To investigate the effect of exogenous as well as endogenous glucagon-like peptide 1 (GLP-1) on postprandial glucose excursions and to characterize the secretion of incretin hormones in type 1 diabetic patients with and without residual b-cell function. RESEARCH DESIGN AND METHODS—Eight type 1 diabetic patients with (T1D+), eight without (T1D2) residual b-cell func-tion, and eight healthy matched control subjects were studied during a mixed meal with concomitant infusion of GLP-1 (1.2 pmol/kg/min), saline, or exendin 9-39 (300 pmol/kg/min). Before the meal, half dose of usual fast-acting insulin was injected. Plasma glucose (PG), glucagon, C-peptide, total GLP-1, intact glucose-dependent insulinotropic polypeptide (GIP), free fatty acids, triglycerides, and gastric emptying rate (GE) by plasma acetaminophen were measured

Symmetries of Electrostatic Interaction between DNA Molecules

We study a model for pair interaction $U$ of DNA molecules generated by the discrete dipole moments of base-pairs and the charges of phosphate groups, and find noncommutative group of eighth order ${\cal S}$ of symmetries that leave $U$ invariant. We classify the minima using group ${\cal S}$ and employ numerical methods for finding them. The minima may correspond to several cholesteric phases, as well as phases formed by cross-like conformations of molecules at an angle close to $\rm{90}^{o}$, "snowflake phase". The results depend on the effective charge $Q$ of the phosphate group which can be modified by the polycations or the ions of metals. The snowflake phase could exist for $Q$ above the threshold $Q_C$. Below $Q_C$ there could be several cholesteric phases. Close to $Q_C$ the snowflake phase could change into the cholesteric one at constant distance between adjacent molecules.Comment: 13 pages, 4 figure

A twist in chiral interaction between biological helices

Using an exact solution for the pair interaction potential, we show that long, rigid, chiral molecules with helical surface charge patterns have a preferential interaxial angle ~((RH)^1/2)/L, where L is the length of the molecules, R is the closest distance between their axes, and H is the helical pitch. Estimates based on this formula suggest a solution for the puzzle of small interaxial angles in a-helix bundles and in cholesteric phases of DNA.Comment: 7 pages, 2 figures, PDF file onl