Synthesis of the C28 through C38 segment of okadaic acid using vinylogous urethane aldol chemistry: Part IV

Dankwardt, John W.; Dankwardt, Sharon M.; Schlessinger, R. H.

doi:10.1016/s0040-4039(98)00974-5

Cited by 22 publications

(12 citation statements)

References 21 publications

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“…In order to understand the stereochemical implications, the lithiated (15,17) and silylated (16,18) enamine derivatives shown in Scheme 5 were studied thoroughly by NMR spectroscopy, and compounds 15 and 17 were investigated by X-ray crystal structure analysis. 11…”

Section: Methodsmentioning

confidence: 99%

“…Condensation of the enolate prepared from enamine 29 and lithium diisopropylamide with methacrolein led to the corresponding syn-vinylogous lactone in 91% yield, with a high level of enantio-and diastereoselectivity. 17 Use of trans-2,5-dimethylpyrrolidine for bulk synthesis remained a problem, so the search for other amines to use in its place continued. As a substitute for chiral 2,5-dimethylpyrrolidine, the C 2 -symmetric amine 41 was developed as a chiral auxiliary for asymmetric induction.…”

Section: Scheme 11mentioning

confidence: 99%

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Reaction of Linear Push-Pull Enamines at the β′-Position

Kostyuk¹,

Volochnyuk²,

Sibgatulin³

2008

Synthesis

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Enamine tautomerism is often the main cause of regioselectivity problems in the chemistry of enamines derived from ketones. Linear push-pull tertiary enamines featuring a methyl (methylene) group at the a-position do not experience such tautomerism; nevertheless, a number of reactions proceed with participation of the methyl (methylene) group. It was our objective to analyze all known reactions of this type and show their high synthetic potential. 1 Introduction 2 Electrophilic Functionalization of Preformed Lithiated or Silylated Enamines 3 Uncatalyzed Reactions of Monoelectrophilic Reagents at the Methyl (Methylene) Group 4 Reactions Proceeding at Both the band b¢-Carbon of the Enamine 5 Reactions Proceeding at the a-Methyl (Methylene) Group and b-Functional Group 6 Conclusion

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Section: Methodsmentioning

confidence: 99%

Section: Scheme 11mentioning

confidence: 99%

Reaction of Linear Push-Pull Enamines at the β′-Position

Kostyuk¹,

Volochnyuk²,

Sibgatulin³

2008

Synthesis

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“…The chiral auxiliary is then removed in two steps involving a 1,4 reduction followed by a Cope elimination [23][24][25] (Scheme 9). The Schlessinger group have described various synthetic applications, including the four main fragments of okadaic acid, [23] (+)-phomolactone, (+)-acetylphomolactone, and (+)-asperlin, as illustrated in Scheme 10. [25] Scheme 8.…”

Section: 3) Aldol Reactions With Vinylogous Urethanesmentioning

confidence: 99%

Synthetic Approaches to α,β‐Unsaturated δ‐Lactones and Lactols

2006

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The synthesis of six‐membered unsaturated δ‐lactones has generated considerable interest, due to their occurrence in a large number of natural products possessing potent biological activities. This microreview attempts to illustrate the different strategies used to obtain such compounds, with a special emphasis on catalytic and asymmetric approaches. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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“…The merit of four-carbon enolates has been demonstrated in many prior synthetic applications . Enolates derived from acyclic vinylogous urethanes, in particular, offer malleable functionality upon aldol and acylation reactions . In a previous communication, we disclosed a highly syn -selective second generation vinylogous urethane (VU), 5 , carrying a C4 methyl substituent, which uses a simple and readily prepared nonracemic auxiliary.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Syn-Selective Aldol Reactions of γ-Oxygenated Vinylogous Urethane with a Second Generation Chiral Auxiliary: Application in Construction of (+)-3-Deoxy-d-manno-2-octulosonic Acid

Schlessinger

Pettus

1998

J. Org. Chem.

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Various examples of highly diastereoselective aldol reactions are presented where the nonracemic lithium enolate 6 derived from a C4-oxygenated vinylogous urethane reacts in syn fashion to provide upon intramolecular lactonization useful γ-alkoxy-δ-lactone synthons 12a−f. In one particular example, the result of reaction with an acrolein surrogate, the lactone product 12e is applied in an efficient asymmetric synthesis of (+)-KDO (10 steps, 34% overall yield). Notable transformations include (1) hydrolysis of the vinylogous urethane functionality, (2) stereoselective reduction of the resulting β-keto-lactone 2, (3) stereoselective dihydroxylation of the vinyl side chain of δ-lactone 17, and (4) addition of α-ethoxy-vinyllithium to the lactone carbonyl of 19 to procure the aldulosonic acid residue in 1 upon ozonolysis.

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Synthesis of the C28 through C38 segment of okadaic acid using vinylogous urethane aldol chemistry: Part IV

Cited by 22 publications

References 21 publications

Reaction of Linear Push-Pull Enamines at the β′-Position

Reaction of Linear Push-Pull Enamines at the β′-Position

Synthetic Approaches to α,β‐Unsaturated δ‐Lactones and Lactols

Asymmetric Syn-Selective Aldol Reactions of γ-Oxygenated Vinylogous Urethane with a Second Generation Chiral Auxiliary: Application in Construction of (+)-3-Deoxy-d-manno-2-octulosonic Acid

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