scholarly journals REGRAS: an auxiliary program for pattern recognition and substructure elucidation of monoterpenes

2001 ◽  
Vol 15 (2) ◽  
pp. 65-98 ◽  
Author(s):  
Marcelo J. P. Ferreira ◽  
Gilberto V. Rodrigues ◽  
AntÔnio J. C. Brant ◽  
Vicente P. Emerenciano
Keyword(s):  
Pattern Recognition ◽  
Chemical Shift ◽  
Nmr Data ◽  
Auxiliary Program ◽  
C Nmr

The main purpose of this paper is to present a procedure that utilizes13C NMR for pattern recognition and substructure elucidation of monoterpenes. By this reason, a novel version of the REGRAS program was developed for the specialist SISTEMAT system. This program carries out an analysis of the13C NMR data from a given compound and, from characteristic chemical shift ranges, recognizes the substructures and the skeleton present in a compound. At the end of this procedure, the program displays as analysis results the likely skeletons and substructures of the substance in question. The REGRAS program was tested on skeleton elucidation of 30 monoterpenes from the most varied skeleton types, exhibiting excellent results in skeleton and substructure prediction processes.

15N and 13C nuclear magnetic resonance of deoxydinucleotide monophosphates. II. Protonation of the homo dimers deoxycytidylyl-(3′,5′)-deoxycytidine, thymidylyl-(3′,5′)-thymidine, and deoxyadenylyl-(3′,5′)-deoxyadenosine in dimethyl sulfoxide

1990 ◽  
Vol 68 (11) ◽  
pp. 2033-2038 ◽  
Author(s):  
Giovanna Barbarella ◽  
Massimo Luigi Capobianco ◽  
Luisa Tondelli ◽  
Vitaliano Tugnoli
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Dimethyl Sulfoxide ◽  
Phosphate Group ◽  
Nmr Data ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Nuclear Magnetic

The preferential protonation sites of the homo dimers deoxycytidylyl-(3′,5′)-deoxycytidine, thymidylyl-(3′,5′)-thymidine, and deoxyadenylyl-(3′,5′)-deoxyadenosine were established by nitrogen-15 and carbon-13 NMR in dimethyl sulfoxide, in the presence of varying amounts of CF3COOH. The nitrogen-15 NMR data show that in d(CpC) the capability of the two N3 nitrogens to accept the proton is slightly different. In d(TpT) and d(ApA) the protonation of the phosphate group leads to significant variations of the chemical shift of the carbons adjacent to phosphorus. Keywords: deoxydinucleotides, protonation, 15N and 13C NMR.

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

scholarly journals A permutation approach to the assignment of the configuration to diastereomeric tetrads by comparison of experimental and ab initio calculated differences in NMR data

2017 ◽  
Vol 13 ◽  
pp. 2478-2485 ◽  
Author(s):  
Przemysław J Boratyński
Keyword(s):  
Chemical Shift ◽  
Ab Initio ◽  
Nmr Data ◽  
Experimental Chemical Shift ◽  
C Nmr ◽  
Chemical Shift Deviations

Scoring permutations of experimental chemical shift deviations and DFT/GIAO calculated deviations of isotropic shieldings for sets of four diastereomers can help to assign their relative configurations. This method was exercised on a set of diastereomeric Cinchona alkaloid derivatives, where 13C NMR data always identified the proper configuration. The presented approach is also an attempt to quantify the assignment by exclusion.

Carbon-13 nuclear magnetic resonance spectra of organic sulfur compounds. Substituent chemical shift (s.c.s.) effects in the 4-thiazoline-2-thione series

1976 ◽  
Vol 54 (10) ◽  
pp. 1660-1664 ◽  
Author(s):  
I. W. J. Still ◽  
N. Plavac ◽  
D. M. McKinnon ◽  
M. S. Chauhan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Sulfur Compounds ◽  
Organic Sulfur ◽  
Organic Sulfur Compounds ◽  
Nmr Data ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr ◽  
Magnetic Resonance Spectra

13C nmr data have been obtained for a series of 4-thiazoline-2-thiones. Substituent chemical shift (s.c.s.) effects for methyl and phenyl substitution have been collated and are discussed in comparison with s.c.s. effects in other heterocyclic systems. Some attempt has also been made to compare our data with those reported previously for the thiazoles and for some thiones in the isothiazole series.

scholarly journals Configurational Study of Diastereoisomeric Royleanone Diterpenoids From Salvia concolor

2019 ◽  
Vol 14 (7) ◽  
pp. 1934578X1986265
Author(s):  
Mónica Díaz-Fernández ◽  
María I. Salazar ◽  
Pedro Joseph-Nathan ◽  
Eleuterio Burgueño-Tapia
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Absolute Configuration ◽  
Vibrational Circular Dichroism ◽  
Chemical Shift Assignments ◽  
Aerial Parts ◽  
Nmr Data ◽  
Nmr Chemical Shift Assignments ◽  
C Nmr

The known diterpenoids horminone (1) and taxoquinone (2) as a mixture, and pure 6,7-dehydroroyleanone (7) were isolated from the aerial parts of not yet studied Salvia concolor Lamb. Although 1 and 2 are known, the 1H Nuclear Magnetic Resonance (NMR) data of their acetyl derivatives 4 to 6 are only partially described. Moreover, the 13C NMR data assignments for 4 and 6 show some inconsistencies and reveal better agreement with those we obtained for diastereoisomeric 3 and 5. Since stereochemical aspects were in doubt, it was considered as mandatory to unambiguously determine the absolute configuration of 3 to 6 using vibrational circular dichroism spectroscopy, which then allowed the complete 1H and 13C NMR chemical shift assignments of 4 to 6.

scholarly journals Use of13C-NMR as complementar identification tool in essential oil analysis

1997 ◽  
Vol 13 (4) ◽  
pp. 265-273 ◽  
Author(s):  
José Wilson Alencar ◽  
Maria Goretti de Vasconcelos Silva ◽  
Maria Iracema Lacerda Machado ◽  
Afrânio Aragão Craveiro ◽  
Francisco José de Abreu Matos ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Carbon Atom ◽  
Essential Oil ◽  
Chemical Shifts ◽  
Chemical Constituents ◽  
Structural Features ◽  
Oil Analysis ◽  
Nmr Data ◽  
C Nmr ◽  
Identification Tool

A program using13C-NMR data was developed to improve GC/MS identifications of chemical constituents in essential oils. Compiled data uses 2290 and 2370 chemical shifts of 229 monoterpenes and 158 sesquiterpenes, respectively, stored into two reference libraries. Each carbon atom was codified using rules that correlates its chemical shift with structural features of the carbon hybridization and vicinity.

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.

Identification of substituted furyltetrazolyl acetates by means of 13C NMR spectrometry

1984 ◽  
Vol 49 (8) ◽  
pp. 1895-1899 ◽  
Author(s):  
Jan Světlík ◽  
Igor Goljer ◽  
Ľubomír Janda
Keyword(s):  
Chemical Shift ◽  
13C Nmr ◽  
Ring System ◽  
Tetrazole Ring ◽  
Nmr Data ◽  
Nmr Spectrometry ◽  
C Nmr

13C NMR data of a series of 5-[5-(substituted phenyl)-2-furyl]-1- and -2-tetrazolyl acetates are presented. Examination of diagnostic resonances emphasizing particularly those arising from the tetrazole ring system enabled both isomers to be easily distinguished. The chemical shift increment for 5-(2-furyl)-1- and -2-tetrazolyl acetate unit has been deduced.

Carbon-13 nuclear magnetic resonance spectra of organic sulfur compounds. Comparison of chemical shifts for carbonyl and thiocarbonyl compounds in the pyrone, thiopyrone, and pyridone series

1976 ◽  
Vol 54 (2) ◽  
pp. 280-289 ◽  
Author(s):  
I. W. J. Still ◽  
N. Plavac ◽  
D. M. McKinnon ◽  
M. S. Chauhan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Conjugated Systems ◽  
Organic Sulfur Compounds ◽  
Nmr Data ◽  
Nuclear Magnetic Resonance Spectra ◽  
Related Series ◽  
Sulfur Containing ◽  
C Nmr

13C nmr data have been obtained for a series of 2- and 4-pyrones and pyridones, and their sulfur-containing analogues. Correlations have been observed between the nature of the ring hetero-atom and the chemical shift difference (Δδ) for the Cα and Cβ carbons in these conjugated systems. No significant correlation, however, appears to exist between the chemical shifts of the C=O and C=S groups. Substituent chemical shift (s.c.s.) effects for various simple substituents are compared with those in related series of compounds.

Glucan isolated from leaves of Althaea officinalis L.

1983 ◽  
Vol 48 (7) ◽  
pp. 2082-2087 ◽  
Author(s):  
Alžbeta Kardošová ◽  
Jozef Rosík ◽  
Rudolf Toman ◽  
Peter Capek
Keyword(s):  
Medicinal Plant ◽  
Periodate Oxidation ◽  
Linear Structure ◽  
Water Soluble ◽  
Partial Hydrolysis ◽  
Methylation Analysis ◽  
Glycosidic Bonds ◽  
Nmr Data ◽  
Althaea Officinalis ◽  
C Nmr

A water-soluble low-molecular D-glucan was isolated from leaves of the medicinal plant marsh-mallow (Althaea officinalis L.). The results of methylation analysis, partial hydrolysis, periodate oxidation, and 13C NMR data indicated a virtually linear structure with α-(1→6) glycosidic bonds.

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