Carbon-13 nuclear magnetic resonance spectra of D-homoandrostane derivatives

The ¹³C chemical shift data of a series of ketone, alcohol and ester derivatives of D-homoandrostane are reported. Homologation effects are discussed, as well as substituent effects on the homologated structures.     

Carbon-13 nuclear magnetic resonance spectra of some aromatic diterpenoids

¹³C n.m.r. studies of a series of tricarbocyclic ring C aromatic diterpenoids using proton-noise and single-frequency off-resonance decoupling, partially relaxed Fourier transform techniques, shift reagents and specifically labelled derivatives have permitted unequivocal assignments of almost all signals. The shieldings caused by oxygenation of C-18 and C-19 and by introduction of various substituents in the aromatic ring are discussed. It is concluded that the ¹³C n.m.r. data are sufficiently characteristic to allow stereochemical assignments. Some effects of deuterium substitution on the carbon resonances are presented.     

Carbon-13 nuclear magnetic resonance spectra of some heterocyclic D-homoandrostanes

The ¹³C chemical shift data of several D-homoandrostanes with heteroatoms (N,O) in the 17a-position are reported. Heteroatom effects on the shieldings of the carbons of rings C and D are discussed.     

Carbon-13 nuclear magnetic resonance spectra of some 2-substituted tetrahydropyrans

Fourier transform carbon-13 nuclear magnetic resonance spectra have been obtained and interpreted for some 2-substituted tetrahydropyrans. The effects of the substituents on α, β, γ and δ-carbon atoms are discussed. Using suitable reference compounds the γ-parameter can be used for quantitative conformational analysis.     

Carbon-13 nuclear magnetic resonance spectra of some mesoionic xanthine analogs

Natural abundance ¹³C NMR chemical shifts have been experimentally determined for a series of mesoionic thiazolo[3,2-a]pyrimidine-5,7-diones. The spectral data are compared with those of related mesoionic dihydrothiazolo[3,2-a]pyrimidine-5,7-diones and mesoionic 1,3,4-thiadiazolo[3,2-a]pyrimidine-5,7-diones. Resonable correlation between the observed ¹³C NMR chemical shifts and CNDO/2 total charge densities have been obtained for the different carbon atoms of 8-methylthiazolo[3,2-a]pyrimidine-5,7-dione.     

Carbon-13 nuclear magnetic resonance spectra of fentanyl analogs

Natural abundance carbon-13 chemical shifts are reported for the hydrochloride salts of fentanyl ( 1a ) and fifteen analogs. The signals are assigned on the basis of chemical shift theory, SFORD multiplicities, signal intensities, comparisons with model compounds, and thiophene carbon-proton coupling constants. In addition to its forensic value, the data suggest that the solution conformations of the analogs are similar to that of fentanyl hydrochloride.     

Carbon-13 nuclear magnetic resonance spectra of veratrine components

The ¹³C NMR spectra were determined and signals assigned to the various carbons of veratridine and cevadine.     

Carbon-13 nuclear magnetic resonance spectra of substituted-s-triazolyl tetrazoles

The natural abundance carbon-13 nuclear magnetic resonance spectra of various 5-aryltetrazoles, 1-(5-aryltetrazol-2-ylacetyl)-4-phenyl thiosemicarbazides and 5-(5-aryltetrazol-2-ylmethyl)-4-phenyl-s-triazole-3-thiols were recorded using Fourier transform techniques. The chemical shifts of various carbon resonances have been assigned on the basis of chemical shift theory, the signal multiplicity observed in the single-frequency off-resonance decoupled (SFORD) spectra and comparison with the chemical shifts of the model compounds.     

Carbon-13 nuclear magnetic resonance of some derivatives of 3-methyl-4,1-benzoxazepine-2,5-dione

Summary ¹³C chemical shift assignment of seven N-derivatives of 3-methyl-4,1-benzoxazepine-2,5-dione is reported. The assignment has been done with the help of J-modulated spectra and by comparison with the values of resembling segments reported in the reference. It has been found that the substituent on nitrogen atom has no significant effect on the¹³C chemical shift of the skeleton.

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¹³C-NMR einiger Derivative des 3-Methyl-4,1-benzoxazepin-2,5-dions

Zusammenfassung Es werden die¹³C-NMR-Verschiebungszuordnungen von sieben N-Derivaten von 3-Methyl-4,1-benzoxazepin-2,5-dionen diskutiert. Die Zuordnungen erfolgten über J-modulierte Spektren und Vergleich von entsprechenden Literaturdaten ähnlicher Molekülsegmente. Es zeigte sich, daß die Substitution am Stickstoff keinen signifikanten Einfluß auf die¹³C-chemischen Verschiebungen der Skelettkohlenstoffatome hat.

     

Carbon-13 nuclear magnetic resonance spectra of methaqualone metabolites

Carbon-13 chemical shifts are reported for methaqualone, seven hydroxylated methaqualone metabolites, and four acetate derivatives. The signals are assigned on the basis of chemical shift theory, SFORD multiplicities, signal intensities, and comparisons with model compounds.     

Carbon-13 nuclear magnetic resonance spectra of phenycyclidine analogs

Natural abundance carbon-13 chemical shifts are reported for the hydrochloride salts of phencyclidine ( 1a ) and sixteen analogs. The signals are assigned on the basis of chemical shift theory, SFORD multiplicities, signal intensities, and comparisons with model compounds. In addition to its forensic value, the data suggests that the solution conformations of the analogs are similar to that of phencyclidine hydrochloride.     

Carbon-13 nuclear magnetic resonance spectra of isoquinoline alkaloids

The ¹³C nmr ehemieal shifts of 1,2,3,4-tetrahydroisoquinoline, salsolidine and laudanosine are reported. The various carbon resonances have been assigned on the basis of chemical shift theory, intensity of the signals, multiplicities generated in SFORD spectra and the comparison with model compounds.     

Carbon-13 nuclear magnetic resonance spectra of ceveratrum alkaloids

The ¹³C NMR spectra were determined and signals assigned to the various carbons of the alkamines veracevine, germine and zygacine derived from steroidal alkaloids of the ceveratrum class. Assignment of signals was aided by analysis of the partially relaxed spectrum of cervagenine 9,12,14-orthoacetate-3, 16-diacetate.     

Carbon-13 magnetic resonance spectra of cocaine metabolites and derivatives

The carbon-13 nmr spectral assignments oi cocaine, O-benzoylecgonine, ecgonine, norcocaine, O-benzylnorecgonine, norecgonine, and N-allylnorcocaine were made. The assignments were primarily based on the correlation of substituent effects within series and selective proton irradiation studies.     

Carbon-13 nuclear magnetic resonance spectra of some methyl and phenyl substituted 2H-azirines

Carbon-13 n.m.r. spectra have been obtained for some methyl and phenyl substituted 2H-azirines. The higher field resonance of C-2 than that of the corresponding aziridine carbon is interpreted in terms of ring strain. Substituent effects on the chemical shifts of the azirine ring carbons are discussed. A set of additivity parameters for the methyl and phenyl groups are obtained which can be used for the calculation of the chemical shifts of the azirine ring carbons. The substituent effect of an azirine ring on the chemical shift of benzene is also discussed in comparison with those of some other substituents. A high degree of s character (48.5%) in the exocyclic orbital of C-3 is indicated by a large J(¹³C-3,H) value (242.5 Hz).     

Carbon-13 nuclear magnetic resonance spectra of methyl 2-pyronecarboxylates

The ¹³C NMR spectra of methyl 2-pyrone-3-, 4-, 5- and 6-carboxylates were studied and the substituent effects on the 2-pyrone ring were compared with those of some model compounds. ¹H NMR spectra were also recorded and discussed. The long range ¹³C, ¹H coupling constants were obtained, discussed and proved useful in signal assignments.