A stereoselective transformation of pseudoindoxyls into oxindoles in a single operation

Güller, Rolf; Borschberg, Hans‐Jürg

doi:10.1016/s0040-4039(00)75984-3

Cited by 23 publications

(11 citation statements)

References 18 publications

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“…Additionally, the oxidation 32a of 2-aryl-substituted indoles has also given us direct access to 3-hydroxy-3H-indoles 73 and related structures. It should be noted that the formation of 3-hydroxy-3H-indoles 73 is not a dead-end since related 2-alkyl systems are known to have the potential to be completely converted into the corresponding oxindoles, 35 and our observations with 2-aryltryptamine derivatives are consistent with these findings. Significantly, the results outlined in Scheme 20 establish unequivocally the potential of using a 2-aryltryptamine derivative as a versatile precursor for the C-3a-C-7¢(aryl) substructure of interest.…”

Section: Scheme 19supporting

confidence: 86%

New Strategies for the Synthesis of Hexahydropyrroloindole Alkaloids Inspired by Biosynthetic Hypotheses

Schmidt¹,

Movassaghi²

2008

Synlett

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Section: Scheme 19supporting

confidence: 86%

New Strategies for the Synthesis of Hexahydropyrroloindole Alkaloids Inspired by Biosynthetic Hypotheses

Schmidt¹,

Movassaghi²

2008

Synlett

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“…Hydroxyindolenine 28 rearranges with heating using Sc(OTf) 3 over 2 hours to afford pseudoindoxyl 33 (Figure 4C) instead of the desired spirooxindole. The equilibrium between pseudoindoxyls and spirooxindoles is well recognized and has been studied for the migration of C2 alkyl substituents by Borschberg 28 and recently for C2 aryl substituents by Movassaghi and coworkers 29 . However, despite prolonged heating, further rearrangement of pseudoindoxyl 33 to the desired spirooxindole was not observed.…”

Section: Resultsmentioning

confidence: 99%

Total synthesis and isolation of citrinalin and cyclopiamine congeners

Mercado-Marin

García-Reynaga

Romminger

et al. 2014

Nature

151

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It is said that carbon, the most abundant element in organic matter, supplies life’s quantity, whereas nitrogen supplies its quality. It is therefore unsurprising that many natural products that contain basic nitrogens (alkaloids) are coveted for their benefit to human health. However, nitrogen is known to mire many chemical syntheses because of its basicity and susceptibility to oxidation. This challenge may be heightened by the presence of more than one nitrogen atom in a targeted complex alkaloid, but can be met by the selective introduction and removal of functional groups that mitigate basicity, as highlighted herein with the first chemical syntheses of citrinalin B and cyclopiamine B. The chemical connections that have been realized as a result of these syntheses, in addition to the isolation of both 17-hydroxycitrinalin B and citrinalin C through 13C feeding studies, supports the existence of a common bicyclo[2.2.2]diazaoctane containing biogenetic precursor to these compounds as has been proposed previously.

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“…Yet another route to 68 was discovered by serendipity, when we investigated whether aristotelone (58) can be transformed back into its precursor serratoline (57) under the influence of Lewis acids [45]. As it turned out, an equilibrium in favour of the latter component is gradually set up when either compound was treated with BF 3 .…”

Section: Aristotelia Alkaloidsmentioning

confidence: 98%

New Strategies for the Synthesis of Monoterpene Indole Alkaloids

Borschberg

2005

COC

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The synthetic efforts of the author's research team in several areas within the monoterpene indole alkaloid family are summarized. Most of the work was accomplished in the field of the Aristotelia alkaloids, where some 25 natural products were synthesized for the first time. Systematic investigations on the oxidative rearrangement of indoles to oxindoles and pseudoindoxyl derivatives led to control over the chemoselectivity and stereoselectivity of this process, which served for enantioselective preparations of the simple alkaloids horsfiline and elacomine. In addition, recent developments in a novel approach to Iboga alkaloids containing a hydroxyl group at C(19) are presented. The key steps involved a self-immolating 1,4-chirality transfer in an Ireland-Claisen rearrangement and an intramolecular nitrone-olefin [2+3]-cycloaddition to give the aliphatic isoquinuclidine core of the target molecules. The first synthesis of (19R)hydroxyibogamine was completed by grafting a 3-ethylindole unit onto the aliphatic nitrogen, followed by closing the 7membered ring.

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A stereoselective transformation of pseudoindoxyls into oxindoles in a single operation

Cited by 23 publications

References 18 publications

New Strategies for the Synthesis of Hexahydropyrroloindole Alkaloids Inspired by Biosynthetic Hypotheses

New Strategies for the Synthesis of Hexahydropyrroloindole Alkaloids Inspired by Biosynthetic Hypotheses

Total synthesis and isolation of citrinalin and cyclopiamine congeners

New Strategies for the Synthesis of Monoterpene Indole Alkaloids

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