Construction of the ABCE-ring structure of talatisamine via decarboxylative radical cyclization

Minagawa, Kosuke; Kamakura, Daiki; Hagiwara, Koichi; Inoue, M.

doi:10.1016/j.tet.2020.131385

Cited by 13 publications

(7 citation statements)

References 48 publications

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“…Inspired by that work, we envisioned that if tributyltin hydride is replaced by allyltributyltin, it would be possible to achieve a radical allylation reaction (Keck allylation) (eq 2). It is worth mentioning that both the bridgehead radicals and the C–C bond formation based on α-aminoalkyl radicals are well documented . However, very few examples of the generation - reduction of bridgehead N -α-carbon radicals have been reported, , and to our knowledge, the Keck allylation has not been applied to the bridgehead α-aminoalkyl radicals.…”

Section: Resultsmentioning

confidence: 99%

Enantioselective Total Syntheses of the Proposed and Revised Structures of Methoxystemofoline: A Stereochemical Revision

et al. 2021

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This article describes the full details of our synthetic efforts toward the enantioselective total synthesis of the complex alkaloid methoxystemofoline. The enantioselective construction of the tetracyclic core features: (1) the Keck allylation at the N-α bridgehead carbon to forge the tetrasubstituted stereocenter; (2) an olefin cross-metathesis reaction for the side-chain elongation that is amenable for the synthesis of congeners and analogues; and(3) a regioselective aldol addition reaction with methyl pyruvate that ensured the subsequent regioselective cyclization reaction to construct the fourth ring. Overman's method was employed to install the 5-(alkoxyalky1idene)-3-methyl-tetronate moiety. In the last step, a nonstereoselective reaction resulted in the formation of both the proposed structure of methoxystemofoline and its Estereoisomer, the natural product (revised structure), in a 1:1 ratio. We suggest to rename the natural product as isomethoxystemofoline, and report for the first time the complete 1 H NMR data for this natural product.

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Section: Resultsmentioning

confidence: 99%

Enantioselective Total Syntheses of the Proposed and Revised Structures of Methoxystemofoline: A Stereochemical Revision

et al. 2021

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“…A recent application of this reagent system developed by Yoshimi was demonstrated by Inoue and co-workers for the synthesis of talatisamine precursor compound 96 (Scheme 33). 79 The group was seeking to find a more efficient means to construct the complex ABCE-ring scaffold of 96 through an intramolecular decarboxylative Giese-type process. Intermediate 96 has the potential to be used toward the synthesis of C 19 -diterpenoid alkaloid talatisamine ( 97 ) and other derivatives.…”

Section: Photocatalysismentioning

confidence: 99%

Direct decarboxylative Giese reactions

2022

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“…In general, carboxylic acids are practically advantageous as radical precursors for photocatalytic reactions because they do not require the preparation of preactivated precursors. Nevertheless, direct decarboxylative reactions are rarely applied to highly complex structures. , Hence, the cyclization conditions were optimized by tuning catalysts, solvents, and bases, and applied to 10 (Table S3). The photoinduced reaction was performed using crude carboxylic acid 10 with iridium(III) complex 21 (10 mol %) and K 2 HPO 4 (5.0 equiv) in DMSO (0.03 M) at 50 °C, leading to tricyclic enone 22 (50% NMR yield) via the 7- endo cyclization and the subsequent base-induced β-elimination of the C1-OTBS group.…”

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confidence: 99%

Total Synthesis of Resiniferatoxin Enabled by Photocatalytic Decarboxylative Radical Cyclization

et al. 2022

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Resiniferatoxin (1) is a complex daphnane diterpenoid with a highly oxygenated 5/7/6-membered ABC-ring system. Here we report a new synthetic route to 1 that requires 27 steps from a starting d-ribose derivative. The carbon spacer and A-ring are sequentially attached to the C-ring by radical allylation and Stille coupling reactions, respectively. An Ir(III)-catalyzed photoinduced decarboxylative radical reaction then forged the sterically hindered bond between the tetra- and trisubstituted carbons to cyclize the central seven-membered B-ring.

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Construction of the ABCE-ring structure of talatisamine via decarboxylative radical cyclization

Cited by 13 publications

References 48 publications

Enantioselective Total Syntheses of the Proposed and Revised Structures of Methoxystemofoline: A Stereochemical Revision

Enantioselective Total Syntheses of the Proposed and Revised Structures of Methoxystemofoline: A Stereochemical Revision

Direct decarboxylative Giese reactions

Total Synthesis of Resiniferatoxin Enabled by Photocatalytic Decarboxylative Radical Cyclization

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