An enantioconvergent route to carbocyclic nucleosides (–)-aristeromycin and (–)-neplanocin a via the asymmetric Diels–Alder reaction

Arai, Yasuhiko; Hayashi, Yoshikazu; Yamamoto, Masatoshi; Takayema, H.; Koizumi, Toru

doi:10.1039/p19880003133

Cited by 34 publications

(8 citation statements)

References 18 publications

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“…Polycyclic alkaloids, such as (+)-carnegine ( 344) and (+)-canadine (345), can be prepared by intramolecular amination of vinylsulfinyl bonds in spite of the fact that this process is not always stereoselective. 316,317 Monocyclic (+)-and ( 7)-sedamines were synthesised 316 from linear precursors, viz., substituted (E )-and (Z )-alkenyl sulfoxides.…”

Section: B Addition Of Heteronucleophilesmentioning

confidence: 99%

Sulfones and sulfoxides in the total synthesis of biologically active natural compounds

Prilezhaeva¹

2000

Russ. Chem. Rev.

185

103

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A graphical treatment of the tone reproduction problem in television systems satisfactorily answered by extensive experimental work, using the techniques of subjective appraisal which have been increasingly developed in recent years. Direct comparison of a reproduction and an original, with all the parameters of the system accurately known, calls, of course, for a considerable experimental effort. Such limited observations as have been made, however, suggest that the shape of the curves at least gives a good impression of the relative effects of viewing cathode-ray tubes with different values of A, and operating under, different conditions. It is not intended to draw any conclusions or express any as to what form of reproduction characteristic is most desirable. There can, however, be little doubt that there are instances where faithful reproduction is not desirable -where, in fact, the television system can improve on the eye and convey the maximum of information or enhance the asthetic value of a scene by emphasizing certain luminosity differences at the expense of others. To a large extent the value of such distortions must be a matter of personal preference.What constitutes the most desirable form of characteristic is, again, a question which calls for large-scale experiment on a subjective basis; factors such as signal-to-noise ratio and the effect of the characteristic on apparent definition have to be taken into account.Reference may be made in passing to the results of Jones's investigation into the preferences of a large number of observers in the matter of photographic prints.Q) This investigation tends to show that preferred prints are those in which the gradient of the logL,/logL, curve is approximately unity for the medium tones, and that a greater fall in the gradient is acceptable towards black. It would be unwise to assume, however, that the results obtained are necessarily applicable to television practice, where the form of the transfer characteristics and the viewing conditions are different. One general principle which does not seem to be in dispute is that, whereas a considerable tolerance exists when the reproduction is in monochrome, colour calls for a much closer approach to fidelity in luminosity reproduction.Large-area luminance range in modern aluminized cathoderay tubes, in the absence of external light, appears to offer little scope for worth-while improvement. It is worth noting, however, that the importance of good detail luminance range in determining the subjective quality of television pictures has been stressed by Law@) and other writers.Assuming that an optimum characteristic, or range of characteristics, can be defined, practical realization of the optimum raises a number of issues, e.g. the relative contributions of the transmitting and receiving apparatus to the overall result, and whether the desired objective can best be arrived at by selection of the camera or cathode-ray tube characteristic or by suitable circuit design.It is hoped that the present communication may help...

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Section: B Addition Of Heteronucleophilesmentioning

confidence: 99%

Sulfones and sulfoxides in the total synthesis of biologically active natural compounds

Prilezhaeva¹

2000

Russ. Chem. Rev.

185

103

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“…When the allylthymine 121 was used as substrate in a cross-metathesis reaction with the commercially available allyl phosphonic acid dimethyl ester (120) under various Scheme (17). conditions (Scheme 19), we obtained either no product or a mixture of two compounds (122, 123) generated from the self-metathesis of 121 and 120, respectively.…”

Section: Scheme (10)mentioning

confidence: 99%

“…Neplanocin A itself was mainly prepared from a bicyclic system, by a chemicoenzymatic approach [16], by an asymmetric Diels-Alder addition of a dienophile to a cyclopentadiene [17], or from the optically pure (+)-γ-lactone-D-ribonic acid, [18]. Other approaches are based on a palladium(0)-catalyzed allylic substitution pioneered by Tsuji and Trost [19] and recently reviewed by our group in the field on nucleoside chemistry [20].…”

Section: Neplanocin Analoguesmentioning

confidence: 99%

Olefin Metathesis Route to Antiviral Nucleosides

Agrofoglio¹,

Nolan²

2005

CTMC

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The success of the early nucleoside agents, the toxicity and metabolic instability of many nucleoside analogues and the effects of viral pathogens on public health are driving the design, synthesis and evaluation of new nucleoside analogues. In this context, a powerful reaction has emerged over the past decade that has fundamentally changed the outlook on nucleoside chemistry: the olefin metathesis reaction. This review is designed to give an overview of the synthesis of some nucleosides of biological interest, according to their structural types (e.g., neplanocins and aristeromycin analogues, 2',3'-unsaturated nucleoside analogues, and acyclonucleosides), using metathesis reactions by employing either the alkoxy imido molybdenum catalyst developed by Schrock and various ruthenium carbene catalysts developed by Grubbs, Hoveyda-Grubbs and Nolan.

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“…Neplanocin A itself can be prepared from a bicyclic system [104] or by an asymmetric Diels-Alder addition of a dienophile to a cyclopentadiene [105]. The most common synthesis of the compound utilises the 2-cyclopenten-1-one, 172, prepared from (+)-γ-lactone-D-ribonic acid, 171, [106,107].…”

Section: ) Carbocyclic L-and/or Unsaturated Nucleosidesmentioning

confidence: 99%

An Overview of Diazine Nucleoside Analogues

Agrofoglio

2006

COC

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Early work on antiviral agents focused on traditional nucleoside analogues in which the base was linked to one or other of the naturally occurring sugars. Some of these were indeed shown to possess anti-metabolic properties, but it became apparent that their usefulness was severely limited by instability and poor selectivity. Since the discovery of the first successful anti-viral drug, acyclovir, in 1974 by Gertrude "Trudy" Elion, interest has diversified towards compounds in which the heterocycle and sugar components of the nucleoside differ significantly from the natural form. These novel types of nucleosides act as anticancer, antiviral or antibacterial drugs. The intense search for clinically useful nucleoside derivatives has resulted in a wealth of new approaches for their synthesis. In this review, we will give an overview of the synthesis of some pyrimidine nucleosides according to their structural types (e.g., acyclics, carbocyclics, and C5-substituted pyrimidine nucleosides), including compounds having "unnatural" L-stereochemistry, along with the synthetic routes of some selected examples. The article also refers to other relevant review articles that have covered particular areas of investigation or have dealt in depth with a single compound.

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An enantioconvergent route to carbocyclic nucleosides (–)-aristeromycin and (–)-neplanocin a via the asymmetric Diels–Alder reaction

Cited by 34 publications

References 18 publications

Sulfones and sulfoxides in the total synthesis of biologically active natural compounds

Sulfones and sulfoxides in the total synthesis of biologically active natural compounds

Olefin Metathesis Route to Antiviral Nucleosides

An Overview of Diazine Nucleoside Analogues

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