MONOREG – an expert system for structural elucidation of monoterpenes

2001 ◽  
Vol 79 (12) ◽  
pp. 1915-1925 ◽  
Author(s):  
Marcelo J Ferreira ◽  
Gilberto V Rodrigues ◽  
Vicente P Emerenciano
Keyword(s):  
Expert System ◽  
Nmr Spectra ◽  
Structural Elucidation ◽  
Structural Determination ◽  
Systematic Data ◽  
Data Analyses ◽  
Nmr Data ◽  
Living Organisms ◽  
C Nmr

This paper describes a new expert system denominated MONOREG for structural determination of monoterpenes. This system is composed of five programs capable of performing 13C NMR spectra data analyses and analyses of systematic data from living organisms. At the end of this procedure, it shows the likely skeletons of the compound in question as well as the substructures compatible with the 13C NMR data. The system was tested on the skeleton elucidation of 40 monoterpenes from a wide variety of structure types and exhibited excellent results in the skeleton prediction process.

Metallkomplexe mit biologisch wichtigen Liganden, XCVI [1] Palladium(II)-, Platin(II)-und Rhodium(I)-Komplexe mit (Phenyl)C-H···Metall-Wechselwirkung von Diphenylmethylen- glycinestern und von 2-Phenyloxazolinonen / Metal Complexes of Biologically Important Ligands, XCVI [1] Palladium(II), Platinum(II) and Rhodium(I) Complexes with (Phenyl)-C-H ··· Metal Interaction of Diphenylmethylene Glycine Esters and from 2-Phenyloxazolones

1997 ◽  
Vol 52 (10) ◽  
pp. 1199-1202 ◽  
Author(s):  
Bernhard Schreiner ◽  
Markus Prem ◽  
Werner Bauer ◽  
Kurt Polborn ◽  
Wolfgang Beck
Keyword(s):  
Metal Complexes ◽  
Nmr Spectra ◽  
Structural Determination ◽  
X Ray ◽  
Metal Interaction ◽  
Close Proximity ◽  
C Nmr

The reactions of Na2PdCl4, [(nBu3P)PtCl2]2, [(nBu3P)PdCl2]2 and [(C8H14)2RhCl]2/CO with diphenylmethylene glycine esters (L1) or 2-phenyl-4-R-oxazolones (L2) afford the complexes (nBu3P)(Cl)2Pt(L1), (OC)2(Cl)Rh(L1), Cl2Pd(L1)2 and (nBu3P)(Cl)2M(L2) (M = Pd, Pt), respectively. The X-ray structural determination of Cl2Pd(L1)2 and the 1H and 13C NMR spectra show a close proximity of the ortho phenyl-H-atom to the metal; the complexes are precursors for ortho metallation.

scholarly journals Ditregra – an auxiliary program for structural determination of diterpenes

1997 ◽  
Vol 13 (3) ◽  
pp. 227-249 ◽  
Author(s):  
Sandra A. Vestri Alvarenga ◽  
Jean Pierre Gastmans ◽  
Gilberto do Vale Rodrigues ◽  
Vicente de Paulo Emerenciano
Keyword(s):  
Expert System ◽  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Heuristic Approach ◽  
Structural Determination ◽  
The Creation ◽  
Auxiliary Program ◽  
C Nmr

This work describes the creation of heuristics rules based on13C-NMR spectroscopy that characterize several skeletal types of diterpenes. Using a collection of 2745 spectra we built a database linked to the expert system SISTEMAT. Several programs were applied to the database in order to discover characteristic signals that identify with a good performance, a large diversity of skeletal types. The heuristic approach used was able to differentiate groups of skeletons based firstly on the number of primary, secondary, tertiary and quaternary carbons, and secondly the program searches, for each group, if there are ranges of chemical shifts that identifies specific skeletal type. The program was checked with 100 new structures recently published and was able to identify the correct skeleton in 65 of the studied cases. When the skeleton has several hundreds of compounds, for example, the labdanes, the program employs the concept of subskeletal, and does not classify in the same group labdanes with double bounds at different positions. The chemical shift ranges for each subskeletal types and the structures of all skeletal types are given. The consultation program can be obtained from the authors.

NMR Determination of the Structure of Peracetylated Icariside B2 from Veratrum Lobelianum BERNH.

1995 ◽  
Vol 60 (8) ◽  
pp. 1380-1385 ◽  
Author(s):  
Václav Suchý ◽  
Miloš Buděšínský ◽  
Karel Ubik ◽  
Daniel Grančai ◽  
Vlasta Földešiová
Keyword(s):  
Detailed Analysis ◽  
Nmr Spectra ◽  
Aerial Part ◽  
C Nmr

rel(1S,4S,5R)-3,3,5-Trimethyl-4-[( 1E)-3-oxo-1-butenyl]-4,5-epoxy-cyclohexyl-O-β-D-glucopyranoside (I) was isolated from the aerial part of Veratrum lobelianum BERNH. The structure was derived mainly from detailed analysis of 1H and 13C NMR spectra of its acetylated derivative II. Compound I has been already reported under the name icariside B2in Epimedium grandiflorum MORR. var. thunbergianum (MIQ.) NAKAI.

Structural Determination of the Hydrofullerene C60D36 by Neutron Diffraction

1998 ◽  
Vol 54 (3) ◽  
pp. 345-350 ◽  
Author(s):  
L. E. Hall ◽  
D. R. McKenzie ◽  
R. L. Davis ◽  
M. I. Attalla ◽  
A. M. Vassallo
Keyword(s):  
Neutron Diffraction ◽  
Density Function ◽  
Diffraction Data ◽  
Fourier Transformation ◽  
Structural Determination ◽  
Molecular Models ◽  
Reduced Density ◽  
C Nmr

A mixture of C60D36 with 24.5 \pm 4.5% C60 by weight has been analysed by neutron diffraction techniques. The diffraction data was converted to a reduced density function G(r) by Fourier transformation. The C60 component of the G(r) was subtracted out. This enabled a comparison for five molecular models of C60D36, with symmetries T, Th , S 6 and two D 3 d isomers, with the experimental G(r). This specimen of C60D36 was found to be best described by a T symmetry isomer, in agreement with 13C NMR and IR data for C60H36 [Attalla et al. (1993). J. Phys. Chem. pp. 6329–6331].

scholarly journals The NMR Spin Systems of Scutellaria 8β,13-Epoxy-neo-clerod-3-en-15,16-olides and Revision of 1H and 13C NMR Spectra Reported Data

2020 ◽  
Vol 15 (10) ◽  
pp. 1934578X2093378
Author(s):  
Josep Coll Toledano
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Spin Systems ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
Nmr Data ◽  
Reported Data ◽  
New Compounds ◽  
C Nmr ◽  
Shielding Effects

The present review of NMR spectroscopic structural elucidation data of new compounds isolated from Scutellaria species is focused on the title compounds, displaying a peculiar 13-spiro feature. It contains a compilation of 1H and 13C NMR data of these diterpenoids grouped by similar substitution patterns. Comparing shielding effects pointed out not only the identity of some compounds (already reported) but also potential misassignments and convenient revisions to get unambiguous structural proposals.

Simple NMR Determination of 5α/5β Configuration of 3-Oxosteroids

2001 ◽  
Vol 66 (10) ◽  
pp. 1529-1544 ◽  
Author(s):  
Hana Chodounská ◽  
Miloš Buděšínský ◽  
Romana Šídová ◽  
Miroslav Šíša ◽  
Alexander Kasal ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Low Frequency ◽  
Simple Method ◽  
H Nmr ◽  
Steroid Skeleton ◽  
C Nmr

A simple method to distinguish the 5α- from the 5β-isomers of 3-oxosteroids based on low-frequency 1H NMR spectra was proposed. Additional 1H and 13C NMR characteristics were derived from the comparison of completely assigned spectra of the 5α- and 5β-isomers. The effect of substitution at different positions of steroid skeleton was evaluated on a series of isomeric 3-oxosteroids, prepared for this purpose.

The determination of the stereochemistry of epoxides located at the 5,6-positions of decalinic systems: An empirical method based on 13C NMR chemical shifts

2002 ◽  
Vol 80 (7) ◽  
pp. 774-778 ◽  
Author(s):  
Raquel M Cravero ◽  
Guillermo R Labadie ◽  
Manuel González Sierra
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Empirical Method ◽  
Nmr Chemical Shifts ◽  
13C Nmr Chemical Shifts ◽  
Empirical Rule ◽  
C Nmr

The 13C NMR spectra of a series of 5,6-epoxides in decalinic systems were studied. The interpretation of the chemical shifts allowed us to formulate an empirical rule to predict the epoxide stereochemistry. A discussion of the scope and limitations of this method and its extension to larger carbon skeletons is also presented.Key words: epoxide stereochemistry, 13C NMR, NMR, decalinic systems, oxiranes.

Structural Determination of an Orphan Natural Product Using Microcrystal Electron Diffraction and Genome Mining

2020 ◽  
Author(s):  
Lee Joon Kim ◽  
Masao Ohashi ◽  
Dan Tan ◽  
Matthew Asay ◽  
Duilio Cascio ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Electron Diffraction ◽  
Natural Product ◽  
Genome Mining ◽  
Precise Determination ◽  
New Drugs ◽  
Structural Determination ◽  
Natural Product Discovery ◽  
Living Organisms

<p>More than 60% of pharmaceuticals are related to natural products (NPs), chemicals produced by living organisms.<a></a> Hence, new methods that accelerate natural product discovery are poised to profoundly impact human health. Of the many challenges that remain in natural product discovery, none are as pervasive as structural elucidation, as determination of the molecular structure of a newly discovered natural product can take months, years, or in some cases be altogether unachievable. This challenge can be fueled by lack of sufficient material for spectroscopic analysis, or difficulties in sourcing the producing organism. Even in cases where the analyte is abundant, its physical properties, including molecular structure, can prevent unambiguous structural determination. Here we report the use of microcrystal electron diffraction (MicroED),<a></a> an emerging cryogenic electron microscopy (CryoEM) technique, in combination with genome mining, to address these challenges. As proof-of-principle, we apply these techniques to fischerin (<b>1</b>), an orphan NP isolated more than 30 years ago, with potent cytotoxicity but ambiguous structural assignment.<a></a> We utilize genome mining methods to reconstruct its biosynthetic pathway and highlight the sensitivity of MicroED through the precise determination of the solid-state structure of <b>1</b> from sub-micron thick crystals. This structural solution serves as a powerful demonstration of the synergy of MicroED and synthetic biology in NP discovery, technologies that when taken together will ultimately accelerate the rate at which new drugs are discovered.</p><div><div><p> </p></div></div>

13C-NMR chemische Verschiebung phenylsubstituierter polycyclischer Kohlenwasserstoffe / 13C-NMR Chemical Shift of Phenylsubstituted Polycyclic Hydrocarbons

1979 ◽  
Vol 34 (11) ◽  
pp. 1334-1343 ◽  
Author(s):  
W. Storek ◽  
J. Sauer ◽  
R. Stößer
Keyword(s):  
Chemical Shift ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Ring Current ◽  
Current Effect ◽  
Nmr Data ◽  
Ring Current Effect ◽  
Anisotropic Contribution ◽  
Chemische Verschiebung ◽  
C Nmr

13C-NMR spectra of tetracene, rubrene, 1,3,5-tri-, penta-, and hexaphenylbenzene are reported. The discussion also includes the already known 13C-NMR data for diphenyl, 9,10-diphenyl-, 9,10-dibenzyl-, and 9,10-dimethyl-anthracene [1] as well as toluene. On the basis of CNDO/2 calculations different influences (diamagnetic and paramagnetic term, anisotropic contribution, ring current effect, geometry) on the chemical shift are analyzed for diphenyl and within the row benzene through tetracene

13 C NMR Spectra of Chromeno-and Prenylated Flavones Structure Revision of Mulberrin, Mulberrochromene, Cyclomulberrin and Cyclomulberrochromene

1978 ◽  
Vol 33 (12) ◽  
pp. 1547-1549 ◽  
Author(s):  
V. Mohan Chari ◽  
Saboor Ahmad ◽  
Bengt-Göran Österdahl
Keyword(s):  
Nmr Spectra ◽  
Nmr Data ◽  
Structure Revision ◽  
Prenylated Flavones ◽  
C Nmr

AbstractReappraisal of the 13C NMR data for mulberrin and mulberrochromene indicate a revision of structure for these two compounds as well as for cyclomulberrin and cyclo-mulberrochromene .

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