Total Synthesis of Bruceolline I

Scarpi, Dina; Faggi, Cristina; Occhiato, Ernesto G.

doi:10.1021/acs.jnatprod.7b00311

Cited by 28 publications

(13 citation statements)

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“…The synthesis of bruceolline H and I entailed (Scheme 23) Sonogashira coupling of suitably protected iodoindole 124, prepared from commercial 121, to obtain propargylic acetate derivative 126. 113 In the presence of the electron-poor [(4-CF 3 C 6 H 4 ) 3 PAu]SbF 6 Au(I) catalyst, this acetate rearranged to generate the required pentadienyl cation with the proper electronic arrangement for Nazarov cyclization. This step provided the cyclopentafused indole 127 in an excellent 82% yield.…”

Section: Cyclopenta[b]indole Alkaloidsmentioning

confidence: 99%

From synthetic control to natural products: a focus on N‐heterocycles

Prandi

Occhiato

2019

Pest Management Science

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Natural products containing a N‐heterocycle motif are widespread in nature and medicinal plants, in particular, have proved to be a source of almost unlimited N‐derived structures with high molecular diversity. Because of their intrinsic potential for use in both biomedical and agricultural applications, there is a general need for new compounds and for the synthesis of ‘natural‐inspired’ analogues. Importantly, transition of a natural product from discovery to a ‘market lead’ is associated with an increasingly challenging demand for more of the compound, which cannot be met by isolation from natural plant sources, often due to low extraction yields and uneven availability of the plant source itself. Synthesis remains the most reliable approach to provide valuable products for the market. In this review, a comprehensive overview of our contribution to synthetic access to N‐derived natural products is given. Major strengths of the proposed methodologies are discussed critically. © 2019 Society of Chemical Industry

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Section: Cyclopenta[b]indole Alkaloidsmentioning

confidence: 99%

From synthetic control to natural products: a focus on N‐heterocycles

Prandi

Occhiato

2019

Pest Management Science

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“…In the framework of our studies on gold(I)-catalyzed reactions of propargyl alcohol derivatives [13][14][15], we have recently reported that the pentannulation of N-heterocycles [16] can be efficiently achieved by a cascade gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives (Figure 1a) [17][18][19][20][21][22][23][24], and we have exploited such a methodology for the synthesis of bruceollines H and I from 3-substituted indoles ( Figure 1b) [25,26]. Our computational study showed that the Nazarov reaction is fast with the 2-substituted piperidine derivatives 1 because of the accelerating effect of the nitrogen atom that stabilizes the oxyallyl cation intermediate 4 formed upon the ring closure.…”

Section: Introductionmentioning

confidence: 99%

Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom

Zanella¹,

Petrović²,

Scarpi³

et al. 2020

Beilstein J. Org. Chem.

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The tandem gold(I)-catalyzed rearrangement/Nazarov reaction of enynyl acetates in which the double bond is embedded in a piperidine ring was computationally and experimentally studied. The theoretical calculations predict that the position of the propargylic acetate substituent has a great impact on the reactivity. In contrast to our previous successful cyclization of the 2-substituted substrates, where the nitrogen favors the formation of the cyclized final product, the substitution at position 3 was computed to have a deleterious effect on the electronic properties of the molecules, increasing the activation barriers of the Nazarov reaction. The sluggish reactivity of 3-substituted piperidines predicted by the calculations was further confirmed by the results obtained with some designed substrates.

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“…Among indole derivatives, cyclopenta[ b ]indoles are of great significance because of their prevalence in a large number of alkaloids possessing wide-ranging biological activities. 5 For example, fischerindole L shows cytotoxicity against HCl-H460 cell lines, 6 terpendole E is an important mitotic kinesin Eg5 inhibitor, 7 yuehchukene possesses anti-fertility and estrogenic activities, 8 bruceollines are traditionally used for treating malaria and other parasitic diseases, 9 paspaline exhibits antibacterial and insecticidal activity, 10 and drugs such as laropiprant, which is believed to have a cholesterol lowering effect, 11 possess a cyclopenta[ b ]indole core, while polyveoline 12 represents an example of natural products having a cyclopenta[ b ]indoline scaffold ( Fig. 1 ).…”

Section: Introductionmentioning

confidence: 99%