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Journal ArticleDOI

Enaminones: versatile intermediates for natural product synthesis*

30 Jun 1999-Pure and Applied Chemistry (International Union of Pure and Applied Chemistry)-Vol. 71, Iss: 6, pp 979-988

AbstractEfforts in our laboratories to devise a general approach to the synthesis of alkaloids focus on the versatile reactivity of enaminones and related compounds containing the structural unit N-CaC-Z (Za COR, CO2R, CN, NO2 ,S O 2Ar, etc.). This lecture presents an overview of our research with these useful building blocks. Themes to be elaborated include chemo- selectivity and diastereoselectivity in reactions of enaminones, and the challenge of controlling absolute stereochemistry.

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Journal ArticleDOI
Abstract: Enaminoketones and esters are gaining increased interest, particularly cyclic-β-enaminoesters, which are known as important intermediates for the synthesis of heterocycles and natural products, because the enantioselective preparation of highly functionalized compounds is of central importance in synthetic chemistry. Enaminones are versatile synthetic intermediates that combine the ambident nucleophilicity of enamines with the ambident eletrophilicity of enones. Enaminoketones and enaminonitriles have proven to be versatile building blocks for the synthesis of various heterocycles such as pyridine, pyrimidine and pyrrole derivatives. Enaminones systems have "enone" character, and may act as acceptors in both 1,2 and 1,4-additions. In this way the enaminone serves as a scaffold for annulation, and can gain access to systems such as pyrroles indolizidines, quinolizidines and perhydroindoles, all of which are common motifs in alkaloid structures. Enaminones are frequently employed as building blocks for the preparation of a variety of bicyclic compounds of biological interest and have been recently recognized as potential anticonvulsant compounds. Since a large number of developments in the use of enaminones in heterocyclic synthesis have occurred, a review of the recent developments in the synthetic approaches, covering the literature since 1995 until 2004, to these interesting molecules and their useful chemical transformations and biological activity can be considered of considerable value.

150 citations


Journal ArticleDOI
Abstract: A variety of β-enamino ketones and esters have been synthesized in high to exellent yields by reacting β-dicarbonyl compounds with amines in the presence of a catalytic amount of indium tribromide. The reaction proceeds smoothly at room temperature in a short reaction time under solvent-free conditions.

117 citations


Journal ArticleDOI
Abstract: Bismuth(III) trifluoroacetate has been found to be an extremely efficient catalyst for the preparation of β-enaminones in water. In addition, by employing this catalyst, high regio- and chemoselective enamination of carbonyl compounds was achieved.

106 citations


Journal ArticleDOI
TL;DR: Although disguised as a 6-endo-dig cyclization, the reagents employed in the transformation play a direct role in bond making and bond breaking, thus changing the mode of addition.
Abstract: A new reaction for the preparation of enaminones has been discovered. This method employs β-amino acids as starting materials to allow diversification as well as incorporation of chirality. The β-amino acids, once converted to ynones, are readily cyclized to the desired six-membered enaminone via a two-step, one-pot protocol. Although disguised as a 6-endo-dig cyclization, the reagents employed in the transformation play a direct role in bond making and bond breaking, thus changing the mode of addition.

80 citations


Journal ArticleDOI
Abstract: A convenient synthesis of 5-oxo-1,2,3,5-tetrahydropyrrolo[1,2- a ]quinoline-4-carboxylic acids, tricyclic analogues of the quinolone antibiotics, is described. Key steps in the route are a novel zinc-mediated Reformatsky reaction between diethyl bromomalonate and N -arylpyrrolidine-2-thiones 18 , and cyclisation of the resulting diethyl pyrrolidinylidenemalonate intermediates 19 in polyphosphoric acid. The products proved to be devoid of biological activity.

77 citations


References
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BookDOI
01 Jan 1991
Abstract: Chapter headings. Carbon-13 and proton NMR shift assignments and physical constants of diterpenoid alkaloids. Supercritical fluid extraction of alkaloids. Recent advances in the total synthesis of amaryllidaceae alkaloids. Applications of radical cyclization reactions in total syntheses of naturally occurring indole alkaloids.

1,262 citations


Book
29 Jun 1993
TL;DR: This paper presents the first total Synthesis of several Natural Products Based On Alkyne-Co2(Co2)6 Complexes, and discusses the design and synthesis of Cooperative "Pinwheel" Fluorescent Sensors, and the application of Silicon-Ass Intramolecular Cross-Coupling.
Abstract: Chapter 1. The Total Synthesis Of Luzopeptins. Chapter 2. Synthesis of Geldanamycin Using Glycolate Aldol Reactions. Chapter 3. From Methylene Bridged Glycoluril Dimers To Cucurbit[N]Uril Analogs With Some Detours Along The Way. Chapter 4. Application Of Silicon-Assisted Intramolecular Cross-Coupling In Total Synthesis Of (+)-Brasilenyne. Chapter 5. Samarium(II) Promoted Ketyl Olefin Cyclizations Applied To The Total Syntheses Of (-)-Steganone And (+)-Isoschizandrin. Chapter 6. The Synthesis Of Polycavernoside A. An Example Of Conformationally Guided Macrolactonization. Chapter 7. First Total Synthesis Of Several Natural Products Based On Alkyne-Co2(Co)6 Complexes. Chapter 8. Total Synthesis Of Myriaporones 1, 3, and 4. Chapter 9. Adventures In Natural Product Synthesis: From Deep Sea Sponge To Pilot Plant. The Large Scale Total Synthesis Of The Marine Natural Product (+)-Discodermolide. Chapter 10. Synthesis Of Aprepitant. Chapter 11. Total Synthesis And Mechanism Of Action Studies On The Antitumor Alkaloid,(-)-Agelastatin A. Chapter 12. Design And Synthesis of Cooperative "Pinwheel" Fluorescent Sensors. Chapter 13. Functionalization Of Pyridines And Thiazoles Via The Halogen-Dance Reaction, Application To The Total Synthesis Of Caerulomycin C And WS75624 B. Chapter 14. Diastereoselective Intramolecular 4+3 Cycloaddition And An Enantioselective Total Synthesis Of (+)-Dactylol.

173 citations


Journal ArticleDOI

40 citations