Asymmetric Synthesis of Polyfunctionalized Pyrrolidines and Related Alkaloids

Pyne, Stephen G.; Davis, Andrew R.; Gates, Nicole J.; Hartley, Joseph P.; Lindsay, Karl B.; Machan, Theeraphan; Tang, Min

doi:10.1055/s-2004-834801

Cited by 133 publications

(27 citation statements)

References 16 publications

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“…105). 348 Although the yield is low, the reaction illustrates several possible reactions: lactone formation, resistance of secondary alcohols to oxidation, imine formation, and ring closure. There is also one example of a tertiary amine being oxidized to a nitroxide.…”

Section: Rearrangement and Oxidation Of Tertiary Allylic Alcoholsmentioning

confidence: 99%

Oxoammonium‐ and Nitroxide‐Catalyzed Oxidations of Alcohols

2009

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The discovery in 1959 of stable nitroxide‐based free radicals such as the prototypical 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) led to their use as electron spin resonance (ESR) spin labels in chemistry, biomedicine, and materials science. These nitroxides are prepared by the oxidation of secondary amines that contain no hydrogen atoms on the alpha‐carbons. The unique redox properties of nitroxides enable their use as oxidants in organic synthesis. The varied preparation and uses of oxoammonium salts as stoichiometric oxidants for alcohols are one subject of this review. Oxoammonium ions as oxidants for alcohols have a number of advantages, for example, the method is heavy‐metal free and some of the reactions can be performed in water or aqueous mixtures. A few side reactions are associated with these oxidations. The most serious is the fast reaction of the oxoammonium ion with free amines The several ways these oxidation reactions can be carried out are discussed in detail. They are: Oxidations using stoichimetric quantities of preformed oxoammonium salts carried out in either acidic, neutral, or basic conditions; reactions in which stoichiometric quantities of oxoammonium salts are generated in situ by disproportionation of a nitroxide in the presence of a strong acid; nitroxide‐catalyzed oxidations using a secondary oxidant; efficient nitroxide‐catalyzed oxidations of primary alcohols to carboxylic acids; and oxidations of primary alcohols or hemiacetals that can lead to lactones.

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Section: Rearrangement and Oxidation Of Tertiary Allylic Alcoholsmentioning

confidence: 99%

Oxoammonium‐ and Nitroxide‐Catalyzed Oxidations of Alcohols

2009

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“…1 The proposed structure of uniflorine A is similar to that of castanospermine 2, except for the stereochemistry at C-1 and the extra hydroxyl substitution at C-2. As part of our program concerned with the synthesis of polyhydroxylated indolizidine and pyrrolizidine alkaloids [4][5][6][7][8][9][10][11] we reported an efficient 9-step synthesis of purported uniflorine A from L-xylose. 10 The structure of our synthetic 1 was unequivocally established by a single-crystal X-ray crystallographic study of its pentaacetate derivative.…”

Section: Introductionmentioning

confidence: 99%

“…Whatever the reasons for the -facial selectivity of 12, this compound and its substituted derivatives have been successfully used by our group, [6][7][8][9]21 and that of Parsons, 23,24 to diastereoselectively prepare polyhydroxylated indolizidine and pyrrolizidine alkaloids and their epimers. When planning our synthesis of 1,2-di-epi-1 we were interested in employing a pyrrolo[1,2-c]oxazin-1-one similar to 14 as a precursor and examining the diastereoselectivity of its DH reactions (Scheme 2).…”

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confidence: 99%

Synthetic and spectroscopic studies on the structures of uniflorines A and B: structural revision to 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine alkaloids

2008

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The diastereoselective synthesis of the C-2 epimer and the C-1, C-2 di-epimers of the putative structure of the alkaloid uniflorine A has been achieved. The synthesis of the latter di-epimers employed a novel pyrrolo[1,2-c]oxazin-1-one precursor to allow for the reversal of π-facial diastereoselectivity in an osmium(VIII)-catalyzed syn-dihydroxylation (DH) reaction. The NMR spectral data of these epimeric compounds and that of related isomers did not match that of the natural product. From a comparison of the NMR data of uniflorines A and B with that of casuarine and the known synthetic 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine isomers we concluded unequivocally that uniflorine B is the known alkaloid casuarine. Although we cannot unequivocally prove the structure of uniflorine A, without access to the original material and data, the published data suggest that the natural product is also a 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine with the same relative C-7-C-7a-C-1-C-2-C-3 stereochemistry as casuarine. We thus suggest that uniflorine A is 6-epi-casuarine. Abstract:The diasteresoselective synthesis of the C-2 epimer and the C-1, C-2 di-epimers of the putative structure of the alkaloid uniflorine A has been achieved. The synthesis of the latter di-

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“…[1] Consequently, the development of robust procedures that enable their preparation with full selectivity control is a major synthetic challenge [2] with great value in chemical biology research. [3] One of the most powerful approaches for the preparation of pyrrolidines is the 1,3-dipolar cycloaddition of azomethine ylides with activated olefins.…”

Section: Introductionmentioning

confidence: 99%

Highly Selective Copper‐Catalyzed Asymmetric [3+2] Cycloaddition of Azomethine Ylides with Acyclic 1,3‐Dienes

González‐Esguevillas

Pascual‐Escudero

Adrio

et al. 2015

Chemistry A European J

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The first examples of the catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides with acyclic activated 1,3-dienes (and 1,3-enynes) are described. Under copper catalysis, a selective cycloaddition at the terminal γ,δ-C=C bond is observed. In addition, depending on the ligand used, either the exo or the endo adduct can be obtained with high selectivity. Under appropriate reaction conditions, the acyclic 1,6-addition product is detected, suggesting a stepwise mechanism. The resulting C4-alkenyl-substituted pyrrolidines are suitable substrates for further access to polycyclic systems, as highlighted by the preparation of hexahydrochromeno[4,3-b]pyrrole and the tetracyclic core of the alkaloid gracilamine.

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Asymmetric Synthesis of Polyfunctionalized Pyrrolidines and Related Alkaloids

Cited by 133 publications

References 16 publications

Oxoammonium‐ and Nitroxide‐Catalyzed Oxidations of Alcohols

Oxoammonium‐ and Nitroxide‐Catalyzed Oxidations of Alcohols

Synthetic and spectroscopic studies on the structures of uniflorines A and B: structural revision to 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine alkaloids

Highly Selective Copper‐Catalyzed Asymmetric [3+2] Cycloaddition of Azomethine Ylides with Acyclic 1,3‐Dienes

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