The acid-catalyzed synthesis of cucurbit[n]urils from formaldehyde and glycoluril is poorly understood. In this paper, we examine a wide range of reaction conditions that include the effects of acid type, acid concentration, reactant concentrations, and temperature to both probe the mechanism and optimize the yields of isolated cucurbit[n]urils, where n = 5−10. A mechanism for the formation of these cucurbit[n]urils is presented. Individual cucurbit[n]urils were unambiguously identified in reaction mixtures using ESMS and 13C NMR.

Controlling factors in the synthesis of cucurbituril and its homologues.

Dicarbonyl (η5-cyclopentadienyl)cobalt functions as a matrix on which a variety of unsaturated organic substrates undergo mutual bond formation. In this way α,ω-diynes cocyclize with monoalkynes to give annelated benzenes, while o-diethynylbenzenes furnish biphenylenes, and α,ω-enynes lead to the formation of complexed bi-and tricyclic dienes. Nitriles cocyclize with two alkynyl groups to give pyridines and other heterocycles, isocyanates allow access to annelated 2-pyridones, and incorporation of carbon monoxide provides complexed cyclopentadienones. In many cases remarkable chemo-, regio-, and stereoselectivity are observed, partially facilitated by use of the trimethylsilyl substituent as a controlling group. The scope and level of maturity of the method are demonstrated by the synthesis of a series of hitherto inaccessible, novel, and theoretically interesting molecules, and by its utilization in several unique approaches to a variety of natural products, e.g. protoberberines, steroids, vitamin B6, and camptothecin.

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Cobalt‐Mediated [2 + 2 + 2]‐Cycloadditions: A Maturing Synthetic Strategy [New Synthetic Methods (43)]

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.

Chemistry and Biology of Taxol

I. Introduction 1485II. Scope of This Review 1485III. Transformations of Cyclobutane Derivatives inOrganic Syntheses1486A. Ring-Opening Reactions 1486B. Ring-Contraction Reactions 1493C. Ring-Expansion Reactions 14951. Five-Membered Rings 14952. Six-Membered Rings 15093. Seven-Membered Rings 15174. Eight-Membered Rings 15215. Nine-Membered Rings 1523IV. Transformations of Cyclobutane Derivatives inNatural Product Syntheses1524A. Ring-Opening Reactions 1524B. Ring-Expansion Reactions 15261. Five-Membered Rings 15262. Six-Membered Rings 15293. Seven-Membered Rings 15324. Eight-Membered Rings 1533V. Conclusion 1534VI. Acknowledgments 1534VII. References 1534

The application of cyclobutane derivatives in organic synthesis.

Enantiomerically pure cyclobutane derivatives and their use in organic synthesis.

Synthese de la chaine du taxol a partir du phenylacetylene avec comme etapes-cle une epoxydation asymetrique et la scission regioselective de l'epoxyde

An efficient, enantioselective synthesis of the taxol side chain

Enantioselective ring construction through asymmetric olefin-ketene cycloaddition. A highly enantiocontrolled approach to (-)-.alpha.-cuparenone and (+)-.beta.-cuparenone

Synthese en 18 etapes a partir de l'acide dichloro-6,6 methyl-3oxo-7bicyclo [3.2.0] heptanecarboxylique-3

Marie Jacqueline Luche

Papers

An efficient, enantioselective synthesis of the taxol side chain

Enantioselective ring construction through asymmetric olefin-ketene cycloaddition. A highly enantiocontrolled approach to (-)-.alpha.-cuparenone and (+)-.beta.-cuparenone

An efficient, enantioconvergent total synthesis of natural hirsutic acid C

Iterative three-carbon annelation. A stereoselective total synthesis of (.+-.)-hirsutic acid C

A short synthesis of the taxotere side chain through dilithiation of boc-benzylamine