Crown cation complex effects. 22. Enhancement of cation binding in lariat ethers bearing a methyl group at the quaternary, pivot carbon atom

1983 ◽  
Vol 48 (8) ◽  
pp. 1237-1242 ◽  
Author(s):  
Yohji Nakatsuji ◽  
Tetsuya Nakamura ◽  
Mitsuo Okahara ◽  
Dennis M. Dishong ◽  
George W. Gokel
Keyword(s):  
Carbon Atom ◽  
Cation Binding ◽  
Lariat Ethers ◽  
Methyl Group ◽  
Cation Complex

Crown cation complex effects. 20. Syntheses and cation binding properties of carbon-pivot lariat ethers

1983 ◽  
Vol 105 (3) ◽  
pp. 586-593 ◽  
Author(s):  
Dennis M. Dishong ◽  
Craig J. Diamond ◽  
Michael I. Cinoman ◽  
George W. Gokel
Keyword(s):  
Cation Binding ◽  
Lariat Ethers ◽  
Binding Properties ◽  
Cation Complex

The biosynthesis of ephedrine

1989 ◽  
Vol 67 (6) ◽  
pp. 998-1009 ◽  
Author(s):  
Gunnar Grue-Sørensen ◽  
Ian D. Spenser
Keyword(s):  
Carbon Atom ◽  
Benzoic Acid ◽  
Pyruvic Acid ◽  
Nmr Spectra ◽  
Carbon Skeleton ◽  
Resonance Spectroscopy ◽  
Methyl Group ◽  
Acid Incorporation ◽  
Group A ◽  
C Nmr

It is shown by 13C nuclear magnetic resonance spectroscopy that the labelled C2 fragment of [2,3-13C2]pyruvic acid is transferred intact into the C-methyl group and the adjacent carbon atom of the Ephedra alkaloids, norephedrine, ephedrine, norpseudoephedrine, and pseudoephedrine, in growing plants of Ephedragerardiana. This finding serves to identify pyruvate as the elusive precursor of the aliphatic C2 terminus of the skeleton of the alkaloids. In earlier experiments with C-labelled substrates, label from [3-14C]pyruvic acid was incorporated mainly, but not exclusively, into the C-methyl group of ephedrine, and label from [2-14C]pyruvate was incorporated similarly into the carbon atom adjacent to the C-methyl group. A C6–C1 unit related to benzaldehyde or benzoic acid has long been known to generate the benzylic fragment of the carbon skeleton of the Ephedra alkaloids. It is likely that the carbon skeleton of ephedrine is generated from pyruvate and either benzaldehyde or benzoic acid, by a reaction analogous to the formation of acetoin or diacetyl from pyruvate and acetaldehyde or acetic acid, respectively. Keywords: biosynthesis of ephedrine, Ephedra alkaloids, 13C NMR spectra, ephedrine, biosynthesis of pyruvic acid, incorporation into ephedrine13C NMR spectra.

Analysis of sodium, potassium, calcium, and ammonium cation binding and selectivity in one- and two-armed nitrogenpivot lariat ethers

1995 ◽  
Vol 5 (1) ◽  
pp. 45-60 ◽  
Author(s):  
Kristin A. Arnold ◽  
Jeanette C. Hernandez ◽  
Chensheng Li ◽  
Jesus V. Mallen ◽  
Akio Nakano ◽  
...  
Keyword(s):  
Ammonium Cation ◽  
Cation Binding ◽  
Lariat Ethers ◽  
Sodium Potassium

The Origin of the Unusual C4ν Structure Predicted for SH4

1994 ◽  
Vol 47 (8) ◽  
pp. 1431 ◽  
Author(s):  
CJ Marsden ◽  
BA Smart
Keyword(s):  
Carbon Atom ◽  
Theoretical Calculations ◽  
Structural Parameters ◽  
Binding Energies ◽  
Molecular Orbital Calculations ◽  
Electrostatic Model ◽  
Net Charge ◽  
Methyl Group ◽  
Steric Factors ◽  
Net Charges

Ab initio molecular orbital calculations have been performed on C2v and C4v isomers of SH4, SF4 and S(CH3)4 to investigate the origin of the different structures adopted by these molecules. We propose an electrostatic model similar in spirit to the VSEPR approach; this implies that the net charges on the ligands L in SL4 compounds can control the geometry of these compounds. Steric factors may also be significant. Even though the net charges on hydrogen and on the CH3 group are similar when these act as ligands towards sulfur, the carbon atom in the methyl group bears a substantial negative net charge, which has important structural consequences. Binding energies and structural parameters are presented for SH4 which are obtained from more complete theoretical calculations than those previously reported.

Novel synthetic access to 15- and 18-membered ring diaza-bibracchial lariat ethers (BiBLEs) and a study of sidearm-macroring cooperativity in cation binding

1986 ◽  
Vol 27 (3) ◽  
pp. 327-330 ◽  
Author(s):  
Vincent J. Gatto ◽  
Kristin A. Arnold ◽  
Anthony M. Viscariello ◽  
Steven R. Miller ◽  
George W. Gokel
Keyword(s):  
Membered Ring ◽  
Cation Binding ◽  
Lariat Ethers

Electrochemical Switching in Reducible Lariat Ethers: from Cation Binding Enhancements to Electrochemically-Mediated Transport

1989 ◽  
pp. 257-266
Author(s):  
Luis Echegoyen ◽  
George W. Gokel ◽  
Lourdes E. Echegoyen ◽  
Zhi-Hong Chen ◽  
Hyunsook Yoo
Keyword(s):  
Cation Binding ◽  
Lariat Ethers
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