Dehydrobromination of methyl 11α-bromo-12-oxopodocarpan-19-oate

1969 ◽  
Vol 47 (19) ◽  
pp. 3661-3670 ◽  
Author(s):  
R. A. Bell ◽  
M. B. Gravestock
Keyword(s):  
Calcium Carbonate ◽  
Nuclear Overhauser Effect ◽  
Hydrogen Bromide ◽  
Keto Acid ◽  
Elimination Process ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
A Minor

The configuration and stereochemistry of methyl 11α-bromo-12-oxopodocarpan-19-oate 1 have been determined by application of the nuclear Overhauser effect. The dehydrobromination of 1 with dimethylacetamide–calcium carbonate results in a predominant 1,4-elimination process which for short reaction periods yields the non-conjugated ketone 8 and for long reaction periods yields the conjugated ketone 2. The 1,2-elimination of hydrogen bromide is a minor process and takes place to the extent of 20–22%. The ketone 8 has been oxidatively cleaved to the keto-acid 11, a valuable intermediate for the synthesis of bicyclic diterpenoids.

Ozonolysis of podocarpic acid

1970 ◽  
Vol 48 (7) ◽  
pp. 1105-1113 ◽  
Author(s):  
R. A. Bell ◽  
M. B. Gravestock
Keyword(s):  
Hydrogen Peroxide ◽  
Methyl Ester ◽  
Methylene Chloride ◽  
Nuclear Overhauser Effect ◽  
High Yield ◽  
Keto Acid ◽  
Dioic Acid ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
Work Up

Low temperature ozonolysis of methyl podocarpate in methanol – methylene chloride results in the formation in high yield of 8β-hydroperoxy-8α-hydroxy-(13 → 17)-pentanorlabd-9(11)-en-12,19-dioic acid 19-methyl ester 8 → 12-lactone 4. Ozonolysis followed by hydrogen peroxide work-up gives the lactone-acid 14a, whilst ozonolysis followed by reduction with sodium borohydride gives keto-acid 3a and lactones 16 and 17 derived from peroxide 4 together with δ-lactone 19 possessing all 18 carbon atoms of methyl podocarpate. The lactone 16 is shown to possess an 8β-configuration by application of the nuclear Overhauser effect.

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

1990 ◽  
Vol 55 (4) ◽  
pp. 1106-1111 ◽  
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.

scholarly journals Cylindromicin from Arctic-Derived Fungus Tolypocladium sp. SCSIO 40433

Molecules ◽  
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.

The isolation, structure, and stereochemistry of traversiadiene. The precursor hydrocarbon of traversianal biosynthesis

1989 ◽  
Vol 67 (8) ◽  
pp. 1302-1304 ◽  
Author(s):  
Albert Stoessl ◽  
G. L. Rock ◽  
J. B. Stothers
Keyword(s):  
Magnetic Resonance ◽  
Biosynthetic Pathway ◽  
Nuclear Overhauser Effect ◽  
Difference Spectra ◽  
Heteronuclear Correlation ◽  
Magnetic Resonance Studies ◽  
Overhauser Effect ◽  
Effect Difference ◽  
Nuclear Overhauser ◽  
Magnetic Resonance Spectra

A tricyclic diene, traversiadiene, isolated from cultures of Cercosporatraversiana has been shown to have the structure and stereochemistry of the previously postulated hydrocarbon intermediate on the biosynthetic pathway to traversianal (1). Detailed:1H and 13C magnetic resonance studies, including homo- and heteronuclear correlation spectra, led to the gross structure, and the stereochemistry was established through a series of nuclear Overhauser effect difference spectra. Keywords: diterpene, traversiadiene, 1H and 13C magnetic resonance spectra.

scholarly journals Contribution of blood to nuclear Overhauser effect at −1.6 ppm

2021 ◽  
Author(s):  
Jing Cui ◽  
Yu Zhao ◽  
Feng Wang ◽  
Daniel F. Gochberg ◽  
Zhongliang Zu
Keyword(s):  
Nuclear Overhauser Effect ◽  
Overhauser Effect ◽  
Nuclear Overhauser
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