75295-95-3Relevant academic research and scientific papers
Synthesis of deuterium-labeled simvastatin
Tian, Lei,Tao, Jie,Chen, Liqin
experimental part, p. 625 - 628 (2011/12/03)
This study describes the synthesis of deuterium-labeled simvastatin. The stable isotope-labeled compound was prepared starting from lovastatin in nine steps with 9% overall yield.
Alkyl Substituent Effect in the Deprotonation of Unsymmetrical Ketones
Johnson, Cris E.,Sannes, Kristin A.,Brauman, John I.
, p. 8827 - 8835 (2007/10/03)
The effect of various degrees of alkyl substitution on the relative rates of deprotonation from the two distinct sites in several unsymmetrical ketones in the gas phase is examined.The infrared multiple photon activation of an appropriately deuterium-labeled alkoxide ion generates the ion-molecule complex for the half-reaction of the bimolecular proton transfer process between an alkyl anion and an unsymmetrical ketone with one deprotonation site selectively deuterated.The resulting products are enolate ions generated by the removal of either a deuteron or a proton and, thus, are distinguishable by mass.The measurement of the enolate ion product ratios, along with an independent measurement of the kinetic isotope effect, allowed the kinetic effect of the alkyl environment on the relative proton transfer rates to be determined.The primary and secondary isotope effects are also estimated from the enolate ion product ratios.By examining the magnitude of the kinetic alkyl effect, the primary isotope effect, and the secondary isotope effect, we learn about the transition state for proton transfer.
The Mechanism of Ethylene Elimination from the Oxonium Ions CH3CH2CH=O+CH2CH3 and (CH3)2C=O+CH2CH3
Bowen, Richard D.,Derrick, Peter J.
, p. 1033 - 1039 (2007/10/02)
The reactions of the metastable oxonium ions CH3CH2CH=O+CH2CH3 and (CH3)2C=O+CH2CH3 are reported and discussed.Various mechanisms for ethylene elimination, which is the principal dissociation route for these ions, are considered.It is shown by means of 2H-labelling experiments and analysis of collision-induced dissociation spectra that routes involving ion-neutral complexes pre-empt 'conventional' mechanisms for these processes.In contrast, the behaviour of the lower homologues CH3CH2CH=OR+ and (CH3)2C=OR+ (R = H, CH3) is consistent with the operation of 'conventional' mechanisms for ethylene expulsion.This contrast is interpreted in energetic terms.The significance of these results for the chemistry of homologous and analogous 'onium' ions containing a Z+-R function (Z = O, S, NH, NCH3; R= CnH2n+1, n 2) is explained.
A Correlation between β-Hydrogen Isotope Effects on Carbon-13 NMR Chemical Shifts in Unsaturated Systems and the Strength of Hyperconjugative Interactions
Arrowsmith, Cheryl H.,Kresge, A. Jerry
, p. 7918 - 7920 (2007/10/02)
β-Hydrogen isotope effects on the carbon-13 NMR chemical shifts of the trigonal carbon in CL3C(R)=X (L=H, or D) are reported for 15 substances inwhich the positive charge density at the trigonal carbon is regulated through systematic variation of R and X.A linear relationship is found between these isotope effects and the chemical shifts of the trigonal carbons, and this is taken as evidence for dependence of the magnitude of these isotope effects upon the strength of the hyperconjugative interaction between CL3 and C(R)=X.An explanation of hyperconjugative NMR isotope effecs in terms of anharmonic carbon-hydrogen bond-bending vibrations is advanced.
Cyclopropane Intermediates in the Rearrangemant and Fragmentation of Olefinic Molecular Ions
Laderoute, Keith R.,Harrison, Alex. G.
, p. 624 - 630 (2007/10/02)
Methyl loss from deuterium-labelled molecular ions of 4-methyl-2-pentene, 2-methyl-2-pentene and 1,1,2-trimethylcyclopropane has been investigated for metastable molecular ions and for molecular ions formed by charge exchange with COS+*, XE+* and CO+*.For metastable ion fragmentation reactions all three compounds exhibit very similar behavior and show specific and essentially equal loss of each of the original methyl groups as well as specific loss of a methyl where the hydrogens derive exclusively from the non-methyl hydrogens of the original molecules.The former results are interpreted in terms of interconversion of the three molecular ions through a ring-opened form of the trimethylcyclopropane molecular ion.The loss of the non-methyl hydrogens as CH3 is interpreted in terms of isomerization to the 2,3-dimethyl-2-butene structure.With increasing internal energy direct allylic cleavage of the unrearranged methylpentene molecular ions increases in importance while the trimethylcyclopropane molecular ion shows an increased preference for loss of the C(2) methyl group.With increasing internal energy loss of the original non-methyl hydrogens as CH3 decreases markedly in importance.
Unimolecular Reactions of Ionized Alkanes
Wendelboe, Jens. F.,Bowen, Richard D.,Williams Dudley H.
, p. 2333 - 2339 (2007/10/02)
The unimolecular reactions of several CnH2n+2+. radical cations are discussed in terms of species involving an incipient carbonium ion coordinated to a radical.These species can be formed by stretching the appropriate bond in the ionized alkane.Subsequent isomerization of the incipient carbonium ion can give rise to rearranged structures in which a 1,2-alkyl shift has effectively occurred.By means of such mechanisms, much of the previously reported data concerning decomposition of ionized n-butane can be explained; in particular, the results of 2H-labeling studies can be interpreted.In addition, new labeling data are reported for ionized n-pentane and isopentane; the results indicate that both 1,2-methyl and 1,2-ethyl shifts precede or accompany dissociation of these C5H12+. species.Previously published 13C- and 2H-labeling data on ionized n-heptane are also considered; these results can be uderstood in terms of competing 1,2-methyl, -ethyl, and -propyl shifts.
