Synthesis of 4‘-Methyl and 4‘-Cyano Carbocyclic 2‘,3‘-Didehydro Nucleoside Analogues via 1,4-Addition to Substituted Cyclopentenones

Hegedus, Louis S.; Cross, Jeff

doi:10.1021/jo040215h

Cited by 13 publications

(4 citation statements)

References 46 publications

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“…Compound 20 , bearing the allylic acetate, a much better nucleofuge than lithium alkoxide, suffered β-elimination to provide 21 with no methylation being observed …”

Section: Resultsmentioning

confidence: 99%

Asymmetric Synthesis of All Eight Seven-Carbon Dipropionate Stereotetrads

2007

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Enantiopure cycloheptadienyl sulfones 6 and 7 are diastereoselectively epoxidized to yield epoxyvinyl sulfones 8, 9, 14, and 16 in high yields and diastereomeric ratios. Syn and anti methylation of epoxides 8, 9, 14, and 16 enables access to all eight possible diastereomeric stereotetrads, seven of which are commonly found in polypropionate natural products. Anti methylations of the above epoxides are possible by either the reaction of methyl organometallics promoted by copper(I), or via reaction with trimethylaluminum to yield stereotetrads 11, 12, 22, and 24. Syn methylations are achieved via Lawton SN2' reaction in the case of stereotetrads 10, 15, and 38, while stereotetrad 13 is accessed by an oxidation/reduction alcohol inversion sequence from stereotetrad 11. All stereotetrads were obtained in high diastereomeric ratios and yields, and their relative stereochemistry was confirmed by X-ray crystallography. Oxidative cleavage of the cyclic stereotetrads yields termini-differentiated acyclic heptanyl stereotetrads ready for use in building larger fragments in the course of target syntheses.

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“…Compound 20 , bearing the allylic acetate, a much better nucleofuge than lithium alkoxide, suffered β-elimination to provide 21 with no methylation being observed …”

Section: Resultsmentioning

confidence: 99%

Asymmetric Synthesis of All Eight Seven-Carbon Dipropionate Stereotetrads

2007

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“…Using the diastereomeric mixture of carbonates and Trost's ligand L1 (see Scheme 22), only the b derivative reacts and the a-derivative remains intact. 30 Neplanocin A, carbovir and aristeromycin (see Fig. 1) have also been prepared using this procedure.…”

Section: Methods Based On Ring-closing Reactionsmentioning

confidence: 99%

Advances in the enantioselective synthesis of carbocyclic nucleosides

et al. 2013

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Carbocyclic nucleosides are nucleoside analogues in which the furanosidic moiety has been replaced by a carbocycle. Several members of this family have been isolated from natural sources and include a 5-membered ring carbocycle. The aim of this review is to examine critically the different methodologies for the enantioselective construction of 3- to 6-membered rings, with a particular focus on 5-membered rings and their modifications. The procedures for bonding the heterocyclic moiety and the carbohydrate are treated separately. The methods for synthesising the carbocyclic moiety mainly focus on the construction of the cycle, although precise details about the functionalisation are provided in some cases. The selected methods aim to provide an overview of the synthesis of carbocycles related to the synthesis of carbocyclic nucleosides. The methods of synthesis of 5-membered rings are classified into two types: methods in which the cyclopentane ring is formed by ring closing reactions (C=C and C-C formation) and methods that start from preformed 5-membered rings, based mainly on cycloaddition reactions. With respect to the methods of synthesis of 3-, 4- and 6-membered ring carbocyclic nucleosides, a selection of the more relevant enantioselective procedures is presented in a systematic manner.

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“…59 Hegedus et al also made use of a chiral auxiliary to control the 1,4-addition of nucleophiles to substituted cyclopentenones (Scheme 32). 60 Addition of Me 2 CuLi/BF 3 •OEt 2 to the enone 141 gave the product 142 in 52% yield and 9 : 1 diastereoselectivity in favour of the desired isomer. The auxiliary was then cleaved with TBAF, but the Luche reduction proceeded with little selectivity and the isomers of 144 needed to be separated.…”

Section: Stereoselective Addition Of a Grignard Reagent To An Enonementioning

confidence: 99%

A review of methods to synthesise 4′-substituted nucleosides

Betson¹,

Allanson²,

Wainwright³

2014

Org. Biomol. Chem.

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Modified nucleosides have received a great deal of attention from the scientific community, either for use as therapeutic agents, diagnostic tools, or as molecular probes. Perhaps the most difficult position of a nucleoside to modify is the 4'-position. Chemists have developed innovative methods to achieve this in a stereoselective manner to allow incorporation of a variety of functional groups. This review provides a summary of the most commonly used or recently published methods for ribose, deoxy-ribose, 4'-thioribose, and carbocyclics.

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Synthesis of 4‘-Methyl and 4‘-Cyano Carbocyclic 2‘,3‘-Didehydro Nucleoside Analogues via 1,4-Addition to Substituted Cyclopentenones

Cited by 13 publications

References 46 publications

Asymmetric Synthesis of All Eight Seven-Carbon Dipropionate Stereotetrads

Asymmetric Synthesis of All Eight Seven-Carbon Dipropionate Stereotetrads

Advances in the enantioselective synthesis of carbocyclic nucleosides

A review of methods to synthesise 4′-substituted nucleosides

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