Chapter 12 The Vinca Alkaloids

Taylor, W. I.

doi:10.1016/s1876-0813(08)60051-2

Cited by 2 publications

(1 citation statement)

References 83 publications

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“…47,48 Thus, the formation of both products can be rationalized considering an initial formation of indolenyl hydroperoxide 4a, which can be reduced to the corresponding 7-hydroxyindolenine 5a (a transformation that can occur spontaneously in the reaction medium) 49 or further rearranged to the keto lactam 6 via a dioxetane intermediate (for a possible mechanism see Figure 2). 50 Although previous work indicated the feasibility of isolation of the indolenyl hydroperoxide 4a, 35,34 we could not isolate it under these conditions, probably because of its rapid decomposition during the purification process. Thus, ibogaine, but not voacangine, reacts with dioxygen in a fundamental state in toluene, probably through a radical mechanism (intermediate A, Figure 2).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Reactivity of the Iboga Skeleton: Oxidation Study of Ibogaine and Voacangine

et al. 2023

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The iboga alkaloids scaffold shows great potential as a pharmacophore in drug candidates for the treatment of neuropsychiatric disorders. Thus, the study of the reactivity of this type of motif is particularly useful for the generation of new analogs suitable for medicinal chemistry goals. In this article, we analyzed the oxidation pattern of ibogaine and voacangine using dioxygen, peroxo compounds, and iodine as oxidizing agents. Special focus was placed on the study of the regio-and stereochemistry of the oxidation processes according to the oxidative agent and starting material. We found that the C 16 -carboxymethyl ester present in voacangine stabilizes the whole molecule toward oxidation in comparison to ibogaine, especially in the indole ring, where 7hydroxy-or 7-peroxy-indolenines can be obtained as oxidation products. Nevertheless, the ester moiety enhances the reactivity of the isoquinuclidinic nitrogen to afford C 3 -oxidized products through a regioselective iminium formation. This differential reactivity between ibogaine and voacangine was rationalized using computational DFT calculations. In addition, using qualitative and quantitative NMR experiments combined with theoretical calculations, the absolute stereochemistry at C 7 in the 7hydroxyindolenine of voacangine was revised to be S, which corrects previous reports proposing an R configuration.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Reactivity of the Iboga Skeleton: Oxidation Study of Ibogaine and Voacangine

et al. 2023

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Treatment of Vinca minor Leaves with Methyl Jasmonate Extensively Alters the Pattern and Composition of Indole Alkaloids

Abouzeid

Beutling²,

Surup³

et al. 2017

J. Nat. Prod.

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Alkaloids extracted from mature Vinca minor leaves were fractionated by preparative HPLC. By means of HRMS and NMR data, the main alkaloids were identified as vincamine, strictamine, 10-hydroxycathofoline, and vincadifformine. Upon treatment with methyl jasmonate (MeJA), the pattern and composition of the indole alkaloids changed extensively. While 10-hydroxycathofoline and strictamine concentrations remained unaltered, vincamine and vincadifformine levels showed a dramatic reduction. Upon MeJA treatment, four other indole alkaloids were detected in high quantities. Three of these alkaloids have been identified as minovincinine, minovincine, and 9-methoxyvincamine. Whereas minovincinine and minovincine are known to occur in trace amounts in V. minor, 9-methoxyvincamine represents a novel natural product. Based on the high similarities of vincamine and 9-methoxyvincamine and their inverse changes in concentrations, it is postulated that vincamine is a precursor of 9-methoxyvincamine. Similarly, vincadifformine seems to be converted first to minovincinine and finally to minovincine. Because MeJA treatment greatly altered the alkaloidal composition of V. minor, it could be used as a potential elicitor of alkaloids that are not produced under normal conditions.

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Chapter 12 The Vinca Alkaloids

Cited by 2 publications

References 83 publications

Reactivity of the Iboga Skeleton: Oxidation Study of Ibogaine and Voacangine

Reactivity of the Iboga Skeleton: Oxidation Study of Ibogaine and Voacangine

Treatment of Vinca minor Leaves with Methyl Jasmonate Extensively Alters the Pattern and Composition of Indole Alkaloids

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