Application of the 2-Azaallyl Anion Cycloaddition Method to an Enantioselective Total Synthesis of (+)-Coccinine

Pearson, William H.; Lian, Brian W.

doi:10.1002/(sici)1521-3773(19980703)37:12<1724::aid-anie1724>3.0.co;2-8

Cited by 40 publications

(2 citation statements)

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“…By using a slightly modified stannyl imine, Pearson and Lian accomplished the total synthesis of (+)-coccinine (Scheme ). Specifically, treatment of stannane 230 with n -BuLi followed by aqueous workup gave the perhydroindole 231 , which was subjected to Pictet–Spengler cyclization conditions to generate 232 . Elimination of the sulfoxide group ( 233 ) followed by inversion of the hydroxyl group gave the desired alkaloid (+)-coccinine.…”

Section: -Azaallyl Anionsmentioning

confidence: 99%

2-Azaallyl Anions, 2-Azaallyl Cations, 2-Azaallyl Radicals, and Azomethine Ylides

et al. 2018

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This review covers the use of 2-azaallyl anions, 2-azaallyl cations, and 2-azaallyl radicals in organic synthesis up through June 2018. Particular attention is paid to both foundational studies and recent advances over the past decade involving semistabilized and nonstabilized 2-azaallyl anions as key intermediates in various carbon–carbon and carbon–heteroatom bond-forming processes. Both transition-metal-catalyzed and transition-metal-free transformations are covered. Azomethine ylides, which have received significant attention elsewhere, are discussed briefly with the primary focus on critical comparisons with 2-azaallyl anions in regard to generation and use.

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Section: -Azaallyl Anionsmentioning

confidence: 99%

2-Azaallyl Anions, 2-Azaallyl Cations, 2-Azaallyl Radicals, and Azomethine Ylides

et al. 2018

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“…The unique structural features and promising biological activities associated with montanine-type AA and their low content in plant material have attracted considerable synthetic efforts [29,30,39,40,49,[74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91]. However, most synthetic approaches involve many steps and low yield.…”

Section: Preparation Of Montanine-type Alkaloids By Rearrangement Of Haemanthamine-type Ring Systemmentioning

confidence: 99%

Chemical and Biological Aspects of Montanine-Type Alkaloids Isolated from Plants of the Amaryllidaceae Family

et al. 2020

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Plants of the Amaryllidaceae family are promising therapeutic tools for human diseases and have been used as alternative medicines. The specific secondary metabolites of this plant family, called Amaryllidaceae alkaloids (AA), have attracted considerable attention due to their interesting pharmacological activities. One of them, galantamine, is already used in the therapy of Alzheimer’s disease as a long acting, selective, reversible inhibitor of acetylcholinesterase. One group of AA is the montanine-type, such as montanine, pancracine and others, which share a 5,11-methanomorphanthridine core. So far, only 14 montanine-type alkaloids have been isolated. Compared with other structural-types of AA, montanine-type alkaloids are predominantly present in plants in low concentrations, but some of them display promising biological properties, especially in vitro cytotoxic activity against different cancerous cell lines. The present review aims to summarize comprehensively the research that has been published on the Amaryllidaceae alkaloids of montanine-type.

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Asymmetric Dihydroxylation of Alkenes

2005

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The oxidation of alkenes to vicinal diols using osmium tetroxide is one of the most selective and reliable transformations in organic synthesis. The reaction stereospecifically produces a cis‐1,2‐glycol and is tolerant of a wide array of functional groups. Methods have been developed to oxidize alkenes stoichiometrically, as well as in the presence of catalytic amounts of osmium tetroxide, when a suitable secondary oxidant is present. The latter process is particularly useful considering the expense and toxicity of osmium tetroxide. The utility of dihydroxylation in organic synthesis is enhanced by the facile transformations of the cis‐1,2‐diol products into other useful derivatives. Among the most versatile intermediates are the corresponding cyclic sulfates, which serve as reactive epoxide equivalents that can be used singly or doubly displaced with amine‐, oxygen‐, sulfur‐, or carbon‐based nucleophiles. The reaction of osmium tetroxide with alkenes is accelerated by several orders of magnitude in the presence of coordinating amine ligands such as triethylamine, quinuclidine, or diazobicyclooctane. The logical extension to asymmetric osmylation of alkenes in the presence of chiral amine bases spurred the study of asymmetric dihydroxylation. The breakthrough of catalytic turnover in the cinchona alkaloid‐osmium tetroxide system revolutionized the field of asymmetric dihydroxylation. Specialized ligands have been developed to provide position selectivity in the dihydroxylation of polyenes, efficient kinetic resolution of racemic substrates, and high levels of enantioselectivity for each of six alkene classes.

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Application of the 2-Azaallyl Anion Cycloaddition Method to an Enantioselective Total Synthesis of (+)-Coccinine

Abstract: A highly functionalized perhydroindole is formed by the intramolecular [π4s+π2s] cycloaddition of a 2-azaallyl anion with a vinyl sulfide [Eq. (a)]. This is the key step in the total synthesis of (+)-coccinine, the enantiomer of the Amaryllidaceae alkaloid (-)-coccinine.

Cited by 40 publications

References 4 publications

2-Azaallyl Anions, 2-Azaallyl Cations, 2-Azaallyl Radicals, and Azomethine Ylides

2-Azaallyl Anions, 2-Azaallyl Cations, 2-Azaallyl Radicals, and Azomethine Ylides

Chemical and Biological Aspects of Montanine-Type Alkaloids Isolated from Plants of the Amaryllidaceae Family

Asymmetric Dihydroxylation of Alkenes

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