scispace - formally typeset
Search or ask a question
Journal ArticleDOI

A short and convenient way to produce the Taxol A-ring utilizing the Shapiro reaction

TL;DR: In this paper, a Taxol A-ring building block was converted in three simple steps to various arenesulfonylhydrazones and then to the target molecule with the Shapiro reaction.
About: This article is published in Tetrahedron.The article was published on 2002-03-11 and is currently open access. It has received 27 citations till now. The article focuses on the topics: Shapiro reaction.

Summary (1 min read)

1. Introduction

  • The authors have earlier reported their entries to the side chain 2 6 and the C-ring precursor 4.
  • The use of intramolecular electrophiles allows preparation of cyclic products with high stereoselectivity.
  • The route involves only four steps and proceeds with high yields.

2. Results and discussion

  • Methylation (13a!14a) was incomplete in these experiments.
  • Also, TMEDA/hexane was impracticable here because of strong salt formation between CH 3 I and TMEDA.

3. Conclusions

  • Taxole A-ring building block 10 was synthesized with a novel and short method consisting of only four steps with high 38% overall yield.
  • Tosylhydrazone 9a was found to be the best of the studied arylhydrazones in Shapiro reaction allowing the formation of stable dianions and complete methylation.
  • Evidence of the possible effect of steric hindrance was observed in the preparation and reactivity of hydrazones.
  • Protonation of the vinyl anion by THF remained problematic to some extent giving always some protonated vinyl anion.
  • This can be minimized with rapid decomposition of dianion 15a at room temperature followed by immediate addition of the electrophile.

Did you find this useful? Give us your feedback

Citations
More filters
Journal ArticleDOI
TL;DR: In this paper, 14 5-ethylidenehydantoins and their derivatives were compared with 14 analogues with 14 different derivatives, including 14 5EHDs with 14 derivatives.

1 citations

Book ChapterDOI
01 Jan 2014
TL;DR: The nitrogen derivatives of carbonyl compounds, such as oximes and hydrazones, are an important class of compounds due to their versatile high reactivity and various methods for the conversion of these nitrogen derivatives have been developed as discussed by the authors.
Abstract: The nitrogen derivatives of carbonyl compounds, such as oximes and hydrazones, are an important class of compounds due to their versatile high reactivity. Over the past 20 years, various methods for the conversion of these nitrogen derivatives have been developed. This chapter describes recent significant advances in this field since the publication of the first edition of Comprehensive Organic Synthesis in 1991. The first section summarizes new methods for the Beckmann rearrangement of oximes to primary or secondary amides promoted by transition metal catalysts or organocatalysts. In the second and third sections, representative examples of the Bamford–Stevens and Shapiro reactions of arenesulfonylhydrazones into various olefinic compounds are described. The final section summarizes recent significant advances in the Neber reactions of oxime sulfonates into α-amino ketones via isolable 2 H -azirine intermediates.

1 citations

Journal ArticleDOI
11 Dec 2020

1 citations

Journal ArticleDOI
Xiaolei Zhu1, Liwei Zou1, Yongting Xu1, Jing Han1, Chenglu Zhang1 
TL;DR: The title compound, C20H30N2O4S, crystallizes as an E isomer with respect to the C=N bond as mentioned in this paper, where the cyclohexane and dioxane rings adopt distorted chair conformations.
Abstract: The title compound, C20H30N2O4S, crystallizes as an E isomer with respect to the C=N bond. Both the cyclo­hexane and the dioxane rings adopt distorted chair conformations. In the crystal structure, mol­ecules form dimers via inversion-related S=O⋯H—N hydrogen bonds. Additional C—H⋯O hydrogen bonds link these units into stacks down the b axis.

Cites background or methods from "A short and convenient way to produ..."

  • ...Tosylhydrazone is recognized as a key intermediate in the synthesis of many natural products (Chamberlin et al., 1978), such as terpenes and taxol (Fabris et al., 1999; Törmäkangas et al., 2002)....

    [...]

  • ...Related literature For background to the use of tosylhydrazones in synthesis, see: Chamberlin et al. (1978); Fabris et al. (1999); Törmäkangas et al. (2002)....

    [...]

  • ...The synthesis of 3 3,7,7-teramethyl-8-(tosylhydrazono)-1,5-dioxaspiro[5,5]undecane was done according to the procedure reported by Törmäkangas et al. (2002) with 1,3-cryclohexanedione as substrate which reacted with MeI to afford 2,2-dimethyl-1,3-cryclohexanedione in 58% yield....

    [...]

Journal ArticleDOI
TL;DR: In this paper, 3,3,7, 7,9-pentamethyl-1,5-dioxaspiro[5.5]undecan-8-one was synthesized and characterized by 1H, 13C NMR, and several kinds of 2D NMR experiments.
References
More filters
Book
01 Jun 1977
TL;DR: Localized Chemical bonding Delocalized Chemical Bonding Bonding Weaker than Covalent Stereochemistry Carbocations, Carbanions, Free Radicals, Carbenes and Nitrenes Mechanisms and Methods of Determining them Photochemistry Acids and Bases Effects of Structure on Reactivity Aliphatic Nucleophilic Substitution Aromatic Electrophilic Substitutes Aliphatically Electrophilic Substitution Free-Radical Substitution Addition to Carbon-Carbon Multiple Bonds Adding to Carbon Hetero Multiple Bonds Eliminations Rearrangements Ox
Abstract: Localized Chemical bonding Delocalized Chemical Bonding Bonding Weaker than Covalent Stereochemistry Carbocations, Carbanions, Free Radicals, Carbenes and Nitrenes Mechanisms and Methods of Determining Them Photochemistry Acids and Bases Effects of Structure on Reactivity Aliphatic Nucleophilic Substitution Aromatic Electrophilic Substitution Aliphatic Electrophilic Substitution Free-Radical Substitution Addition to Carbon-Carbon Multiple Bonds Addition to Carbon- Hetero Multiple Bonds Eliminations Rearrangements Oxidations and Reductions The Literature of Organic Chemistry Classifications of Reactions by Type of Compound Synthesized.

4,885 citations

Journal ArticleDOI
TL;DR: This account attempts to bring together in a cogent overview the chemistry and biology of taxol, one of the few organic compounds, which, like benzene and aspirin, is recognizable by name to the average citizen.
Abstract: One can view plants as a reference library of compounds waiting to be searched by a chemist who is looking for a particular property. Taxol, a complex polyoxygenated diterpene isolated from the Pacific Yew, Taxus brevifolia, was discovered during extensive screening of plant materials for antineoplastic agents during the late 1960s. Over the last two decades, interest in and research related to taxol has slowly grown to the point that the popular press now seems poised to scoop each new development. What was once an obscure compound, of interest only to the most masochistic of synthetic chemists and an equally small number of cellular biologists, has become one of the few organic compounds, which, like benzene and aspirin, is recognizable by name to the average citizen. In parallel, the scientific study of taxol has blossomed. Physicians are currently studying its effects on nearly every known neoplasm. Biologists are using taxol to study the mechanisms of cell function by observing the effects of its interactions with the cellular skeletal systems. Synthetic chemists, absorbed by the molecule's unique and sensitive structure and functionality, are exploring seemingly every available pathway for its synthesis. Indeed, the demand for taxol has risen so in the last five years that alternative sources to the extraction of T. brevifolia are being vigorously pursued. Because of the rapidly expanding scope of research in the multifaceted study of taxol, those who are interested in the field may find acquisition of a reasonable base of knowledge an arduous task. For this reason, this account attempts to bring together, for the first time, in a cogent overview the chemistry and biology of this unique molecule.

554 citations

Journal ArticleDOI
TL;DR: The chemistry of the potent anticancer diterpenoid taxol is reviewed, with an emphasis on isolation and analysis, structural modifications, partial synthesis, and structure-activity relationships.

275 citations

Frequently Asked Questions (1)
Q1. What are the contributions in this paper?

This material is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form.