Pyrrolizidines by Rearrangement of β‐Lactams

Cavagna, Friedrich; Linkies, Adolf; Pietsch, H.; Reuschling, D.

doi:10.1002/anie.198001291

Cited by 11 publications

(4 citation statements)

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“…Their structural and stereochemical complexity, coupled with their diverse and potent biological activities, make pyrrolizidine alkaloids as well as structurally related unnatural compounds very attractive synthetic targets. It has been described that the racemic 6-(2-iodoethyl)-7-oxo-1-azabicyclo[3.2.0]heptane-2,2-dicarboxylic acid diethyl ester 150 on reaction with acids or bases undergoes rearrangement with ring expansion …”

Section: 32 Polycyclic Five-membered Ringsmentioning

confidence: 99%

β-Lactams: Versatile Building Blocks for the Stereoselective Synthesis of Non-β-Lactam Products

2007

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Section: 32 Polycyclic Five-membered Ringsmentioning

confidence: 99%

β-Lactams: Versatile Building Blocks for the Stereoselective Synthesis of Non-β-Lactam Products

2007

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“…The second group of reactions is based on the building of a conveniently functionalized 2-azetidinone to produce different types of usually cyclic compounds by selective bond breakage and rearrangement . Despite the versatility of the 2-azetidinone ring, there is little information available on the use of β-lactams as chiral synthons for the synthesis of pyrrolizidine alkaloids, with only Reuschling and Palomo having reported β-lactam routes to simple pyrrolizidines. At the outset of the present studies, no information was available regarding the 1,3-dipolar cycloaddition reaction involving 4-oxoazetidine-2-carbaldehydes-derived azomethine ylides .…”

Section: Introductionmentioning

confidence: 99%

Rapid and Stereocontrolled Synthesis of Racemic and Optically Pure Highly Functionalized Pyrrolizidine Systems via Rearrangement of 1,3-Dipolar Cycloadducts Derived from 2-Azetidinone-Tethered Azomethine Ylides

et al. 2001

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This work describes a convenient procedure for the straightforward preparation of polyfunctionalized enantiopure pyrrolizidine systems. The methodology capitalizes on a HCl(g)-promoted reaction of the 1,3-dipolar cycloadducts derived from 2-azetidinone-tethered azomethine ylides, smoothly affording different types of highly functionalized bi- and tricyclic systems in racemic and optically pure forms. This process involves a selective bond cleavage of the four-membered ring, followed by a rearrangement under the reaction conditions. The synthetic route employed was shown to be compatible with a variety of 4-oxoazetidine-2-carbaldehydes, alpha-amino esters, or dipolarophiles, offering a versatile entry to pyrrolizidine systems.

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“…The total synthesis of several natural products such as biotin [155], cribrostatin 4 [156], and himandrine [157] has also been carried out using 2-azetidinones as important building blocks. The syntheses of pyrrolizidines [158], fused prolines [159], oxazinones [160], amino glycals [161], aminocyclobutanes [162], bicyclic c-lactams [163], medium-sized heterocycles [164], and complex macrocycles [165] deserve to be mentioned as well.…”

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confidence: 99%

The Chemistry of 2‐Azetidinones (β‐Lactams)

Alcaide¹,

Almendros²,

Luna³

2011

Modern Heterocyclic Chemistry

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The large number of recent reports on b-lactam chemistry demonstrates the increasing interest in this important class of compounds. Monocyclic b-lactams frequently serve as precursors for the synthesis of classical bicyclic b-lactam antibiotics. The cyclic 2-azetidinone skeleton has been extensively used as a template on which to build the heterocyclic structure fused to the four-membered ring, using the chirality and functionalization of the b-lactam nucleus as a stereocontrolling element. The discovery of nonclassical b-lactam antibiotics, such as monobactams and nocardicins, coupled with ever-growing new applications such as enzyme inhibition has triggered a renewed interest in the building of new monocyclic b-lactam derivatives. Besides the utility of b-lactams as biologically active agents, they are used as intermediates in a-and b-amino acid synthesis, as well as building blocks for alkaloids, heterocycles, taxoids and other types of compounds of biological and medicinal interest. Physicochemical Data Computational ChemistryTheoretical studies show that b-lactams are weaker bases, in the gas phase, than acyclic amides [1]. The attenuation of basicity upon cyclization is stronger than that found for cyclic ketones of similar size due to the existence of a negative hyperconjugation effect that is present in b-lactams but not in cyclic ketones. Ab initio calculations indicate that both b-lactams and acyclic amides are oxygen bases, but the gap between the oxygen and nitrogen intrinsic basicities is much smaller in the former due to the aforementioned cyclization effects. This decrease of the oxygen Modern Heterocyclic Chemistry, First Edition. Edited

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Pyrrolizidines by Rearrangement of β‐Lactams

Cited by 11 publications

References 1 publication

β-Lactams: Versatile Building Blocks for the Stereoselective Synthesis of Non-β-Lactam Products

β-Lactams: Versatile Building Blocks for the Stereoselective Synthesis of Non-β-Lactam Products

Rapid and Stereocontrolled Synthesis of Racemic and Optically Pure Highly Functionalized Pyrrolizidine Systems via Rearrangement of 1,3-Dipolar Cycloadducts Derived from 2-Azetidinone-Tethered Azomethine Ylides

The Chemistry of 2‐Azetidinones (β‐Lactams)

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