1H and 13C NMR spectral analysis of some necines of toxic pyrrolizidine alkaloids

Röder, Erhard; Liu, K.; Bourauel, T.

doi:10.1007/bf00321863

Cited by 5 publications

(2 citation statements)

References 9 publications

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“…Thus, the structure of (+)-crotanecine is firmly secured. Until recently, the only 1 H NMR data available for (+)-crotanecine were from the original 60 MHz 1 H NMR spectrum 2 Alkaloids that contain (+)-crotanecine ( 1 ) as the necine base. …”

Section: Introductionmentioning

confidence: 99%

Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 11. The Synthesis of (+)-Crotanecine

Denmark

Thorarensen

1997

J. Am. Chem. Soc.

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(+)-Crotanecine (1) is the necine base component of a number of pyrrolizidine alkaloids. This necine subunit is an amino triol bearing a primary allylic alcohol characterized by an all-cis relationship of its stereocenters. The synthesis of (+)-crotanecine has been accomplished in 10 steps and 10.2% overall yield. The key step in the asymmetric synthesis is a Lewis acid-promoted, tandem inter[4 + 2]/intra[3 + 2] cycloaddition between a (fumaroyloxy)nitroalkene 14 and chiral β-silylvinyl ether (−)-26. This synthesis serves to illustrate the synthetic versatility of the tandem cycloaddition to incorporate additional functionality.

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Section: Introductionmentioning

confidence: 99%

Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 11. The Synthesis of (+)-Crotanecine

Denmark

Thorarensen

1997

J. Am. Chem. Soc.

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“…A thorough analysis of the 1 H and 13 C NMR spectra of these two cis ‐diols led us to propose that the transalpinecine described was not the claimed 1β‐2β‐dihydroxy‐1α‐hydroxymethyl‐8α‐pyrrolizidine. Beyond the difference in chemical shifts, likely due to the protonation variations, the most significant differences in 1 H‐NMR are observed on coupling constants for H‐2 and H‐3 (Table ). The reported NMR spectra ( 1 H and 13 C) of transalpinecine did not match either the other cis ‐diol, 1α,2α‐ 6 .…”

Section: Resultsmentioning

confidence: 99%

Transalpinecine and Analogues: First Total Synthesis, Stereochemical Revision and Biological Evaluation

et al. 2019

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The first total synthesis of transalpinecine, a pyrrolizidine alkaloid extracted from Heliotropium transalpinum is reported. The concise synthetic route developed towards these unusual iminosugar‐like natural compounds relies on an intramolecular Morita–Baylis–Hillman reaction. The four diastereoisomers of transalpinecine, as well as the two diastereoisomers of the parent epoxide subulacine, were prepared. 1H NMR‐based stereochemical assignment of these different diastereoisomers was substantiated by quantum calculations of NMR shifts and coupling constants, allowing revision of the initially reported transalpinecine structure. One of these synthetic compounds significantly potentiates the activity of the F508del‐CFTR corrector VX‐809.

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Enantiospecific total synthesis of (−)-crotanecine

Kothapalli

Puthukanoori

Ranga

et al. 2017

Tetrahedron Letters

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1H and 13C NMR spectral analysis of some necines of toxic pyrrolizidine alkaloids

Cited by 5 publications

References 9 publications

Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 11. The Synthesis of (+)-Crotanecine

Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 11. The Synthesis of (+)-Crotanecine

Transalpinecine and Analogues: First Total Synthesis, Stereochemical Revision and Biological Evaluation

Enantiospecific total synthesis of (−)-crotanecine

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