Structural determination of ε‐lactams by <sup>1</sup>H and <sup>13</sup>C NMR

Montalvo-González, Rubén; Ariza‐Castolo, Armando

doi:10.1002/mrc.2504

Cited by 3 publications

(3 citation statements)

References 24 publications

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“…The 13 C NMR spectrum displayed 23 carbon signals (Table 1) which were assigned using DEPT and HSQC experiments to be four methyls, five methylenes, seven methines and seven quaternary carbons. The latter signals included a characteristic lactam carbonyl group at δ c 173.5 and a ketone carbonyl at δ c 211.5 ppm [8] . The two carbonyl groups were readily assigned to C‐12 and C‐13 of the lactam ring by means of their mutual correlations in the HMBC spectrum with proton H‐9 ( δ H 1.07) in addition to other observed correlations (Figure 2).…”

Section: Resultsmentioning

confidence: 93%

Greenwaylactams A, B and C, the First Group of Sesquiterpene Alkaloids with an Eight‐Membered Lactam Ring from Greenwayodendron oliveri

et al. 2021

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Three new sesquiterpene alkaloids of the polyveoline type containing eight‐membered lactam rings named greenwaylactam A (1), B (2) and C (3) were isolated from the leaves of a Cameroonian medicinal plant Greenwayodendron oliveri (Engl.) Verdc along with three known compounds diacetylpolyveoline (4), N‐acetyl‐8α‐polyveolinone (5) and methyl pheophorbide‐A (6). These comprise the first members of a new class of ξ‐lactam sesquiterpenes. Compounds were isolated by means of successive column chromatographies and their structures were elucidated by extensive NMR spectroscopic analyses and HRESIMS. The configuration of 1 was deduced from its single‐crystal X‐ray diffraction. The crude extract and some isolated compounds were assessed for their antibacterial activity against four enteric bacterial strains Escherichia coli, Salmonelles typhi, Shigella dysenterie and Klebseilla pneumonie using the micro‐dilution method. Compounds 1, 2, 5 and 6 were the most active with MIC values varying between 31.25–250 μg/mL.

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Section: Resultsmentioning

confidence: 93%

Greenwaylactams A, B and C, the First Group of Sesquiterpene Alkaloids with an Eight‐Membered Lactam Ring from Greenwayodendron oliveri

et al. 2021

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“…An unequivocal assignment of the 13 C NMR spectra was made after partial chromatographic separation of isomers 1c, 2b, 3c , and 4c (for instance, see the 13 C NMR spectrum of compound 2b in the supporting material). The N‐aromatic oxaziridines ( 2a–2e and 3a–3e ) were transformed into the corresponding ε ‐lactams as a thermodynamic isomer …”

Section: Resultsmentioning

confidence: 99%

Structural and conformational analysis of 1‐oxaspiro[2.5]octane and 1‐oxa‐2‐azaspiro[2.5]octane derivatives by ¹H, ¹³C, and ¹⁵N NMR

Montalvo-González

Ariza‐Castolo

2012

Magnetic Reson in Chemistry

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A structural and conformational analysis of 1-oxaspiro[2.5]octane and 1-oxa-2-azaspiro[2.5]octane derivatives was performed using (1) H, (13) C, and (15) N NMR spectroscopy. The relative configuration and preferred conformations were determined by analyzing the homonuclear coupling constants and chemical shifts of the protons and carbon atoms in the aliphatic rings. These parameters directly reflected the steric and electronic effects of the substituent bonded to the aliphatic six-membered ring or to C3 or N2. The parameters also were sensitive to the anisotropic positions of these atoms in the three-atom ring. The preferred orientation of the exocyclic substituents directed the oxidative attack.

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“…8 Structural studies of certain alkaloid-analogue-substituted δlactams were conducted in 1994 by Boudreault et al 9 The authors determined the relationships between the substituents in carbons 5 and 6 based on 1 H and 13 C NMR and X-ray crystallography. In 2009, Ariza-Castolo et al 10 published a conformational analysis of N-aryl ε-lactams substituted with alkyl groups based on the analysis of coupling constants and chemical shift data from 1 H and 13 C NMR spectra.…”

Section: Introductionmentioning

confidence: 99%

NMR Spectroscopy and Theoretical Calculations in the Conformational Analysis of 1-Methylpyrrolidin-2-one 3-Halo-derivatives

et al. 2015

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This study reports the results of ab initio and density functional theory (DFT) electronic structure calculations as well as (3)J(HH) experimental and calculated coupling constant data obtained in the investigation of the conformational equilibrium of 3-halo-derivatives of 1-methylpyrrolidin-2-one. The five-membered ring assumes an envelope conformation owing to the plane of formation of the O═C-N-R bond, with C4 forming the "envelope lid". When the conformation changes, the "lid" alternates between positions above and below the amide plane. The α-carbonyl halogen assumes two positions: a pseudo-axial and a pseudo-equatorial. In the gaseous phase, the calculations indicate that the pseudo-axial conformer is more stable and preferable going down the halogen family. Natural bond orbital analysis showed that electronic delocalization is significant only for the iodo derivative. In the other derivatives, the electrostatic repulsion between oxygen and the halogen determines the conformational equilibrium. When the solvated molecule was taken into account, the pseudo-equatorial conformer population increased with the relative permittivity of the solvent. This variation was strong in the fluoro derivative, and the preference was inverted. In the chlorine derivative, the two populations became closer in methanol and acetonitrile. In the bromine and iodine derivatives, the percentage of pseudo-equatorial conformer increased only slightly owing to the dipole moment of the conformation: the pseudo-equatorial conformation has a greater dipole moment and thus is stable in media with high relative permittivity.

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Structural determination of ε‐lactams by ¹H and ¹³C NMR

Cited by 3 publications

References 24 publications

Greenwaylactams A, B and C, the First Group of Sesquiterpene Alkaloids with an Eight‐Membered Lactam Ring from Greenwayodendron oliveri

Greenwaylactams A, B and C, the First Group of Sesquiterpene Alkaloids with an Eight‐Membered Lactam Ring from Greenwayodendron oliveri

Structural and conformational analysis of 1‐oxaspiro[2.5]octane and 1‐oxa‐2‐azaspiro[2.5]octane derivatives by ¹H, ¹³C, and ¹⁵N NMR

NMR Spectroscopy and Theoretical Calculations in the Conformational Analysis of 1-Methylpyrrolidin-2-one 3-Halo-derivatives

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Structural determination of ε‐lactams by 1H and 13C NMR

Cited by 3 publications

References 24 publications

Greenwaylactams A, B and C, the First Group of Sesquiterpene Alkaloids with an Eight‐Membered Lactam Ring from Greenwayodendron oliveri

Greenwaylactams A, B and C, the First Group of Sesquiterpene Alkaloids with an Eight‐Membered Lactam Ring from Greenwayodendron oliveri

Structural and conformational analysis of 1‐oxaspiro[2.5]octane and 1‐oxa‐2‐azaspiro[2.5]octane derivatives by 1H, 13C, and 15N NMR

NMR Spectroscopy and Theoretical Calculations in the Conformational Analysis of 1-Methylpyrrolidin-2-one 3-Halo-derivatives

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Structural determination of ε‐lactams by ¹H and ¹³C NMR

Structural and conformational analysis of 1‐oxaspiro[2.5]octane and 1‐oxa‐2‐azaspiro[2.5]octane derivatives by ¹H, ¹³C, and ¹⁵N NMR