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.

Electrooxidation of 2-arylfurans

1981 ◽  
Vol 46 (4) ◽  
pp. 906-916 ◽  
Author(s):  
Miroslav Janda ◽  
Jan Šrogl ◽  
Hana Dvořáková ◽  
Dalimil Dvořák ◽  
Ivan Stibor
Keyword(s):  
Electronic Spectra ◽  
Nmr Spectra ◽  
Model Compounds ◽  
Methyl Group ◽  
C Nmr

Electrochemical methoxylation of 2-phenylfuran (I) and 2-(4-nitrophenyl)furan (VI) proceeded anomalously, affording 5-methoxy-2-phenylfuran (XI) and 5-methoxy-2-(4-nitrophenyl)furan (XIII), respectively. 2-Phenyl-5-methylfuran (II) and methyl-2-(2-methylphenyl)-3-furoate (VIII) behaved normally giving the respective 2,5-dimethoxy-2,5-dihydrofuran derivatives XII and XIV. The suggested ECNECB mechanism of the anomalous methoxylation was confirmed by methoxylation of compound II, in which the methyl group hinders the last CB step, and also of compound VIII in which the automaticity is suppressed by forced deviation from planarity. Forced deviation from planarity was moreover studied also on 2-(4-methylphenyl)furan (III), 5-methyl-2-(2-methylphenyl)furan (IV) and 3,5-dimethyl-2-(2-methylphenyl)furan (V) as model compounds. For all the derivatives the INDO charges were calculated and correlated with the 1H- and 13C-NMR spectra. The experimental electronic spectra were correlated with the theoretical ones (INDO-S-CI). All the results obtained confirm the suggested mechanism.

Comments on "Librations around the C(S)–phenyl bond in N-thiobenzoylmorpholines observed by 220 MHz proton magnetic resonance spectroscopy"

1977 ◽  
Vol 55 (12) ◽  
pp. 2297-2301 ◽  
Author(s):  
Ulf Berg
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Transition State ◽  
Proton Magnetic Resonance ◽  
Nmr Spectra ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Temperature Dependent ◽  
New Interpretation ◽  
C Nmr

The interpretation of the temperature dependent nmr spectra of the three thiobenzmorpholides 1–3 in terms of torsional libration proposed in the title article is criticized. Pure samples of cis-1 and trans-1 have been prepared and studied by dynamic 1H and 13C nmr. A new interpretation is presented which involves the freezing of the passage over the steric barrier with a planar Ph—C(S)N transition state.

On the chemistry and high field nuclear magnetic resonance spectroscopy of rapamycin

1980 ◽  
Vol 58 (6) ◽  
pp. 579-590 ◽  
Author(s):  
John A. Findlay ◽  
Lajos Radics
Keyword(s):  
High Field ◽  
Nmr Spectra ◽  
Resonance Spectroscopy ◽  
X Ray ◽  
Conformational Isomers ◽  
H Nmr ◽  
Neutral Compounds ◽  
Complete Assignment ◽  
Hydrolysis Of ◽  
C Nmr

Base catalysed hydrolysis of rapamycin (C51H79NO13) affords six neutral compounds identified by chemical and spectroscopic means as 2a, 3b, 3d, 5, 2,4-dimethylphenol, and L(−)-piperidine-2-carboxylic acid 6, and whose generation has been plausibly rationalized. These findings as well as detailed analyses of 13C nmr and 1H nmr spectra provide independent corroboration of the X-ray derived rapamycin crystal structure 1. Structurally homogeneous in the solid state, rapamycin is found to occur in solutions as a mixture of two conformational isomers (approximately 4:1). Through nearly complete assignment of the high field 1H (400 MHz) and 13C (100.6 MHz) nmr spectra, the isomerism is shown to be associated with trans–cis rotation of an amidic bond within the 31-membered macrolide ring. The predominant form corresponds to the conformer portrayed by X-ray analysis.

Alkylated benzimidazole and benzotriazole derivatives of 3-amino-2-propenoic acid

1989 ◽  
Vol 54 (3) ◽  
pp. 713-724 ◽  
Author(s):  
Viktor Milata ◽  
Dušan Ilavský ◽  
Igor Goljer
Keyword(s):  
Hydrogen Atom ◽  
Nmr Spectra ◽  
Model Compounds ◽  
Methyl Group ◽  
Propenoic Acid ◽  
Independent Synthesis ◽  
Amino Derivatives ◽  
Derivatives Of ◽  
Benzotriazole Derivatives ◽  
C Nmr

The alkylation of unsubstituted 3-(5-benzimidazolyl- and 5-benzotriazolyl)amino derivatives of 2-propenoic acid (I) results in the replacement of hydrogen atom at the nitrogen of YZC=CH-NH- substituent (II-IV). The model compounds with a methyl group in the azole nucleus (V-VII) have been prepared by an independent synthesis. The structure of all products has been confirmed and confronted with their IR, UV, 1H and 13C NMR spectra.

scholarly journals Carbon-13 NMR Chemical Shift of Methyl Group: A Useful Parameter for Structural Analysis of C-Methylated Flavonoids

2006 ◽  
Vol 1 (11) ◽  
pp. 1934578X0600101
Author(s):  
Pawan K. Agrawal ◽  
Chandan Agrawal ◽  
Shravan Agrawal
Keyword(s):  
Structural Analysis ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Nmr Chemical Shift ◽  
Methyl Group ◽  
Nmr Chemical Shifts ◽  
Nmr Study ◽  
Pterocarpus Santalinus ◽  
Group A ◽  
C Nmr

The 13C NMR resonances corresponding to the C-Me group of C-6 and/or C-8 C-methylated-flavonoids absorb between 6.7–10.0 ppm and typically between 6.7–8.7 ppm. A comparative 13C NMR study reflects that the 13C NMR chemical shifts reported for 6-hydroxy-5-methyl-3′,4′,5′-trimethoxyaurone-4-O-α-L-rhamnoside from Pterocarpus santalinus and 8-C-methyl-5,7,2′,4′- tetramethoxyflavanone from Terminalia alata are inconsistent with the assigned structures, and therefore need reconsideration.

scholarly journals 13C-nmr Spectroscopy to Monitor Sugars in Pitch of Internodes of a sh2 Corn at Developmental Stages

HortScience ◽  
1998 ◽  
Vol 33 (6) ◽  
pp. 980-983 ◽  
Author(s):  
V.M. Russo ◽  
J. Williamson ◽  
K. Roberts ◽  
J.R. Wright ◽  
N. Maness
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Nmr Spectra ◽  
Developmental Stages ◽  
Sweet Corn ◽  
Resonance Spectroscopy ◽  
C Nmr ◽  
Nuclear Magnetic

Sugars move through stalks to be deposited in kernels in sweet corn (Zea mays L.). Concentrations of sugars in stalks change as plants pass through developmental stages. To follow such changes, carbon-13 nuclear magnetic resonance spectroscopy (C-nmr), a technology that can measure concentrations of sugars in tissues, was compared with analysis by high-performance liquid chromatography (HPLC). A shrunken-2 hybrid (cv. Illini Gold), was monitored from mid-whorl to fresh-market maturity (R3). Internodes near the base of the stalk, just below the ear, and between an ear and the tassel were sampled at each developmental stage. Chemical shifts in C-nmr spectra were measured in parts per million hertz (ppm) down-field relative to tetramethyl silane. Through silk emergence (R1) C-nmr spectra were similar regardless of internode, having line positions between 60 and 105 ppm. Unique lines for glucose, fructose, and sucrose were at 96, 98, and 104 ppm, respectively, and mole fractions were similar to those determined by HPLC. The highest concentrations were recorded at R1 for sucrose (26.1 mg·mL-1), from tasseling (VT) through R3 for fructose (avg. 30.4 mg·mL-1), and from VT to R1 for glucose (avg. 32 mg·mL-1). Carbon-13 nuclear magnetic resonance spectroscopy can be used, with minimal sample handling, to monitor sugar concentrations in sweet corn.

Carbon-13 nuclear magnetic resonance spectra of E-silyl-alkenes

1980 ◽  
Vol 58 (4) ◽  
pp. 361-368 ◽  
Author(s):  
Constantinos A. Tsipis ◽  
Constantinos A. Tsoleridis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Quantitative Analysis ◽  
Nmr Spectroscopy ◽  
Carbon Atom ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr

Carbon-13 nmr chemical shifts of a number of E-silyl-alkenes containing the silyl substituent at an sp2 carbon atom are presented. Assignments of the chemical shifts have been made by noting systematic variations in the spectra with changes in substituents and by comparison of the chemical shifts to those of the corresponding unsubstituted alkenes. The substituent effects observed were explained on the basis of the π-acceptor ability of the silyl substituents and the structure of the molecules. Comparing the 13C nmr spectra of the E-silyl-alkenes and those of the corresponding unsubstituted alkenes, differential chemical shifts have been obtained which can be used as empirical substituent parameters for the prediction of the 13C nmr spectra of other E-silyl-alkenes not yet studied. It was also demonstrated that 13C nmr spectroscopy can be used without resorting to special techniques (gated decoupling and the addition of paramagnetics) as an alternative method to the 1H nmr for the quantitative analysis of mixtures of regio-isomer E-silyl-alkenes.

cis-Cyclohexano-9-crown-3 ether. Solid state and low-temperature solution stereochemistry as determined by X-ray crystallography and nuclear magnetic resonance spectroscopy

1993 ◽  
Vol 71 (7) ◽  
pp. 951-959 ◽  
Author(s):  
G.W. Buchanan ◽  
A.B. Driega ◽  
A. Moghimi ◽  
C. Bensimon ◽  
K. Bourque
Keyword(s):  
Low Temperature ◽  
Nmr Spectra ◽  
Solid Phase ◽  
Resonance Spectroscopy ◽  
Ring Inversion ◽  
X Ray ◽  
Common Features ◽  
X Ray Crystallography ◽  
Temperature Solution ◽  
C Nmr

The X-ray crystal structure of the title material has been determined at −130 °C. Low-temperature 1H1H COSY, 13C1H HETCOR, and DEPT 13C NMR spectra have been recorded, which permit unambiguous assignments of all carbon resonances when ring inversion is slow on the NMR timescale. The limiting low-temperature solution phase 13C spectrum has many common features with the solid phase 13C CPMAS spectrum recorded at 300 K. Spectra for the 7,10-tetra-deuterio derivative have also been obtained and substituent influences on 13C shieldings are discussed in detail.

scholarly journals Synthetic, Infrared, 1H and 13C NMR Spectral Studies on N-(2-/3-Substituted Phenyl)-4-Substituted Benzenesulphonamides, 4-X’C6H4SO2NH(2-/3-XC6H4), where X’ = H, CH3, C2H5, F, Cl or Br, and X = CH3 or Cl

2005 ◽  
Vol 60 (1-2) ◽  
pp. 106-112 ◽  
Author(s):  
B. Thimme Gowda ◽  
Mahesha Shetty ◽  
K. L. Jayalakshmi
Keyword(s):  
Solid State ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Spectral Studies ◽  
1H And 13C Nmr ◽  
Methyl Group ◽  
Benzene Rings ◽  
Stretching Vibrations ◽  
C Nmr

Twenty three N-(2-/3-substituted phenyl)-4-substituted benzenesulphonamides of the general formula, 4-X’C6H4SO2NH(2-/3-XC6H4), where X’ = H, CH3, C2H5, F, Cl or Br and X = CH3 or Cl have been prepared and characterized, and their infrared spectra in the solid state, 1H and 13C NMR spectra in solution were studied. The N-H stretching vibrations, νN−H, absorb in the range 3285 - 3199 cm−1, while the asymmetric and symmetric SO2 vibrations vary in the ranges 1376 - 1309 cm−1 and 1177 - 1148 cm−1, respectively. The S-N and C-N stretching vibrations absorb in the ranges 945 - 893 cm−1 and 1304 - 1168 cm−1, respectively. The compounds do not exhibit particular trends in the variation of these frequencies on substitution either at ortho or meta positions with either a methyl group or Cl. The observed 1H and 13C chemical shifts of are assigned to protons and carbons of the two benzene rings. Incremental shifts of the ring protons and carbons due to -SO2NH(2-/3-XC6H4) groups in C6H5SO2NH(2-/3-XC6H4), and 4- X’C6H4SO2- and 4-X’C6H4SO2NH- groups in 4-X’C6H4SO2NH(C6H5) are computed and employed to calculate the chemical shifts of the ring protons and carbons in the substituted compounds, 4-X’C6H4SO2NH(2-/3-XC6H4). The computed values agree well with the observed chemical shifts.

Synthesis and Conformational Analysis of Disubstituted Sparteine Derivatives

2003 ◽  
Vol 68 (4) ◽  
pp. 696-710 ◽  
Author(s):  
Władysław Boczoń ◽  
Beata Jasiewicz
Keyword(s):  
Carbon Atom ◽  
Conformational Analysis ◽  
Nmr Spectra ◽  
Equatorial Position ◽  
Methyl Group ◽  
Ir And Nmr Spectra

Synthesis of disubstituted sparteine derivatives and their diperchlorate salts was performed. Their IR and NMR spectra were analysed to determine the structure of these compounds, as well as the substituent and the protonation effects. It was shown that both unsaturated (2,17β-dimethyl-2,3-didehydrosparteine (12), 17β-isopropyl-2-methyl-2,3-didehydrosparteine (13)) and saturated (2,17β-dimethylsparteine (14), 17β-isopropyl-2-methylsparteine (15)) newly obtained sparteine derivatives have the same configurational-conformational system: trans A/B chair/chair, trans C/D boat/chair. The methyl and the isopropyl (both equatorial) groups at C-17 appear the elements stabilizing the boat-chair system of the C/D rings, which does not change either on the introduction of the second substituent to the opposite quinolizidine system (the A/B rings) or on protonation. The protonation of the free bases obtained gives only disalts. The atoms undergoing the protonation are either C-3 and N-16 in 12 and 13 or both nitrogen atoms (N-1 and N-16) in 14 and 15. The methyl group introduced on the carbon atom C-2 takes equatorial position, as in 2-methylsparteine (2).

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