Nuclear overhauser effect in coupled-spin systems using selective perturbation

,The structure of the straight silanes SinH2n+2 (1 ≤ n ≤ 7) and of the branched isomers isotetrasilane, iso- and neopentasilane, 2-silyl- and 3-silylpentasilane, 2,3-disilyltetrasilane as well as 2-silyl- and 3-silylhexasilane could be unambiguously elucidated by 29Si NMR spectroscopy. Systematic trends in the chemical shift and coupling parameters were observed and an empirical relationship between δ(29Si) of a 29Si nucleus and the number of the neighbouring silicon atoms in αβor γposition is given. In 1H decoupled spectra the nuclear Overhauser effect on the 29Si resonance was found to increase with increasing distance of the 29Si nucleus from the end of the chain. A complete analysis of the multi spin systems of disilane, trisilane and isotetrasilane was performed and the signs of the 29Si,H- and H,H-long range coupling constants were determined with regard to the negative sign of 1J(29SiH).

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1H NMR studies of [N-MeAib1, Tyr(Me)4]ANGII and [N-MeAib1, Tyr(Me)4, Ile8]ANGII in dimethylsulfoxide by nuclear Overhauser effect (NOE) enhancement spectroscopy: cis-trans Isomerism of the His-Pro bond

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19901106 ◽

1990 ◽

Vol 55 (4) ◽

pp. 1106-1111 ◽

Cited By ~ 1

Author(s):

John Matsoukas ◽

Paul Cordopatis ◽

Raghav Yamdagni ◽

Graham J. Moore

Keyword(s):

1H Nmr ◽

Nuclear Overhauser Effect ◽

Nmr Studies ◽

Restricted Rotation ◽

Overhauser Effect ◽

Major Isomer ◽

Conformational Properties ◽

Nuclear Overhauser

The conformational properties of the Sarmesin analogues [N-MeAib1, Tyr(Me)4]ANGII and [N-MeAib1, Tyr(Me)4, Ile8]ANGII in hexadeutero-dimethysulfoxide were investigated by Nuclear Overhauser Effect (NOE) Enhancement Studies. Cis-trans isomers (ratio 1 : 6) due to restricted rotation of the His-Pro bond were observed. Interresidue interactions between the His Cα proton and the two Pro Cδ protons revealed that the major isomer was the trans.

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Cylindromicin from Arctic-Derived Fungus Tolypocladium sp. SCSIO 40433

Molecules ◽

10.3390/molecules26041080 ◽

2021 ◽

Vol 26 (4) ◽

pp. 1080

Author(s):

Imran Khan ◽

Jing Peng ◽

Zhuangjie Fang ◽

Wei Liu ◽

Wenjun Zhang ◽

...

Keyword(s):

Secondary Metabolites ◽

Nuclear Overhauser Effect ◽

Inhibition Activity ◽

Tyrosinase Inhibition ◽

Bioactive Natural Products ◽

Chemical Structures ◽

Overhauser Effect ◽

Spectroscopic Analyses ◽

Potential Resource ◽

Nuclear Overhauser

The fungus strain SCSIO 40433 was isolated from an Arctic-derived glacier sediment sample and characterized as Tolypocladium cylindrosporum. A new compound, cylindromicin (1), and seven known secondary metabolites (2–8) were isolated from this strain. The chemical structures of these compounds were elucidated by comprehensive spectroscopic analyses. Cylindromicin (1) featured a 3,4-dihydro-2H-pyran skeleton. The absolute configuration of compound 1 was assigned via interpretation of key Nuclear Overhauser Effect Spectroscopy (NOESY) correlations and Electronic Circular Dichroism (ECD) calculation. Cylindromicin (1) exhibited significant tyrosinase inhibition activity. This study highlights Polar fungi as a potential resource for new bioactive natural products.

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