Enantiomerically pure building blocks from sugars. 11. Diels-Alder reactions of pyranoid enolone esters with cyclopentadiene under thermal, Lewis acid catalysis, and high-pressure conditions

Dauben, William G.; Kowalczyk, Bruce A.; Lichtenthaler, Frieder W.

doi:10.1021/jo00295a029

Cited by 26 publications

(20 citation statements)

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“…In the case of ulosides 2a – c , under comparable conditions, applying potassium carbonate as a base in wet toluene at elevated temperatures the enolones 3a – c were isolated in good yields. Carbohydrate‐derived 3,2‐enones and ‐enolones have been used as substrates for a variety of reactions including Diels–Alder reactions or conjugate addition reactions , . Furthermore, interesting biological activities, e.g.…”

Section: Resultsmentioning

confidence: 99%

Carbohydrate‐Derived 3,2‐Enolones in the Base‐Catalyzed Rearrangement to Highly Functionalized C4‐Quaternary 4‐Hydroxy‐2‐cyclopentenones

2017

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3,4,6‐O‐benzylated β‐2‐ulosides were subjected to 3,4‐elimination, providing carbohydrate‐derived 3,2‐enolones. Reaction of these enolones under basic conditions in polar aprotic solvents afforded highly functionalized racemic 5‐alkoxy‐2‐benzyloxy‐4‐benzyloxymethyl‐4‐hydroxy‐2‐cyclopentenones. The influence of the nature of the base as well as solvent effects were investigated. The rearrangement products obtained from this reaction exhibit a 4‐hydroxy‐C4‐quaternary stereogenic center. In contrast, the rearrangement of comparable dihydropyran‐3‐ones was reported to furnish the C5‐quaternary 5‐hydroxy‐2‐cyclopentenones. Plausible mechanisms for the described rearrangement and subsequent isomerization processes are given.

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Section: Resultsmentioning

confidence: 99%

Carbohydrate‐Derived 3,2‐Enolones in the Base‐Catalyzed Rearrangement to Highly Functionalized C4‐Quaternary 4‐Hydroxy‐2‐cyclopentenones

2017

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“…The 1 H NMR spectrum of the conjugated addition product 4 is in agreement with an R configuration for the new stereocenter generated at C-4 (Scheme 1), as the small coupling constants values (J 3a,4 = 5.0 Hz, J 3b,4 = 2.7 Hz, and J 4,5 = 2.0 Hz) indicate that 4-H is equatorially oriented (gauche to 5-H) and that the C-4-4-H bond bisects the angle formed by the methylene protons (3a,3b-H). The high diastereofacial selectivity in the addition reaction in favor of the d-threo isomer may be attributed to the stereocontrol exerted by the axially oriented isopropoxy group in the preferred 0 H 5 conformation of the dihydropyranone, [14,22] which is stabilized by the anomeric effect, that is intensified by the presence of the carbonyl group vicinal to the anomeric center. [23] We have observed a similar selectivity in cycloadditions [14,17] and additions of common thiols to 1.…”

Section: Resultsmentioning

confidence: 99%

Stereoselective Synthesis of 3‐Deoxy‐4‐S‐(1→4)‐Thiodisaccharides and Their Inhibitory Activities Towards β‐Glycoside Hydrolases

2005

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The sulfur linkage of β‐(1→4)‐thiodisaccharides was constructed with excellent diastereoselectivity by Michael addition of 2,3,4,6‐tetra‐O‐acetyl‐1‐thio‐β‐D‐galactose (2) or its β‐D‐glucose isomer (3) to sugar‐derived (2S, 6S)‐6‐acetoxymethyl‐2‐(2‐propyloxy)‐2H‐pyran‐3(6H)‐one (1). These reactions led to the per‐O‐acetyl glycosides of 3‐deoxy‐4‐S‐glycopyranosyl‐4‐thiohexopyranosid‐2‐ulose (4 and 5, respectively). Similar conjugated addition to the enone 1 of the isothiouronium salts 6 or 7, precursors in the synthesis of 2 or 3, also afforded the thiodisaccharides 4 or 5, respectively, with exclusive formation of the isomer that has an R configuration for the C‐4 stereocenter of the reducing‐end. The carbonyl function of 4 and 5 was reduced, and the resulting products were O‐deacetylated to give the free 4‐S(1→4)‐thiodisaccharides 10, 11, 14, and 15, which have a deoxy functionality adjacent to the thio group. These compounds were tested as inhibitors of glycoside hydrolases. Thus 11, the 3‐deoxy‐4‐thiomimetic of Galβ(1→4)Gal, proved to be a competitive inhibitor of the β‐galactosidase from E. coli (Ki = 0.16 mM). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…In terms of selectivity, DA cycloaddition is a well‐known phenomenon that contributes to the expansion of a wide range of compounds with intricate capabilities and controlled stereochemistry [37–39] . Numerous synthetic accomplishments have been established so far with exceptional efficacy based on various selectivity characteristics in order to create top‐notch organic frameworks [40–45] .…”

Section: Selectivity In Diels‐alder Cycloaddition Pathwaymentioning

confidence: 99%

“…In terms of selectivity, DA cycloaddition is a well-known phenomenon that contributes to the expansion of a wide range of compounds with intricate capabilities and controlled stereochemistry. [37][38][39] Numerous synthetic accomplishments have been established so far with exceptional efficacy based on various selectivity characteristics in order to create top-notch organic frameworks. [40][41][42][43][44][45] This review aims to compile the work based on selectivity in cycloaddition protocols to generate a systematic, synthetically valuable composition in organic synthesis, inspired by the distinct results accumulated by the DA reaction.…”

Section: Selectivity In Diels-alder Cycloaddition Pathwaymentioning

confidence: 99%

Regioselectivity Switch Towards the Development of Innovative Diels‐Alder Cycloaddition and Productive Applications in Organic Synthesis

2022

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The Diels‐Alder (DA) reaction is one of the fascinating synthetic strategies known for its pericyclic action and concerted mechanism that leads to various targets. Numerous synthetic pursuits have been rewarded with conceptually distinct and efficient ways. To date, extensive and spectacular accomplishments have been made in the field of Diels‐Alder chemistry to overcome the complexities of organic synthesis that inspired organic chemists to focus on expanding and establishing the postulates. In principle, DA reactions are governed by their straightforward reactivity pattern with a high degree of certainty, primarily attributed to the HOMO‐LUMO separation of reacting partners. Furthermore, general forecasts rely on account of background studies, conveniently hypothesizing the stereochemical outcomes and reaction dynamic pathways. DA has recently emerged as a technique for establishing a variety of products from the same reacting species under varying reaction conditions rather than a general reactivity profile. Such exceptional results are of significant interest in organic synthesis to pursue the challenges of unanticipated product establishment. Herein, we summarize the impressive finding of the remarkable switch in the regioselectivity and diastereoselectivity of DA reactions under a diverse set of reaction protocols in light of Diels‐Alder's unending importance in chemical science. This review aims to establish a beneficial account of Diels‐Alder towards the astonishing switches extended to study varying synthetic versions in organic synthesis protocols attributed to natural and biologically active scaffolds. This review also provides insight into distinct reaction dynamics in DA reactions that are subjected to access molecular frameworks ranging from simple to complicated ones to foster high levels of innovation in chemical sciences.

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Enantiomerically pure building blocks from sugars. 11. Diels-Alder reactions of pyranoid enolone esters with cyclopentadiene under thermal, Lewis acid catalysis, and high-pressure conditions

Cited by 26 publications

References 0 publications

Carbohydrate‐Derived 3,2‐Enolones in the Base‐Catalyzed Rearrangement to Highly Functionalized C4‐Quaternary 4‐Hydroxy‐2‐cyclopentenones

Carbohydrate‐Derived 3,2‐Enolones in the Base‐Catalyzed Rearrangement to Highly Functionalized C4‐Quaternary 4‐Hydroxy‐2‐cyclopentenones

Stereoselective Synthesis of 3‐Deoxy‐4‐S‐(1→4)‐Thiodisaccharides and Their Inhibitory Activities Towards β‐Glycoside Hydrolases

Regioselectivity Switch Towards the Development of Innovative Diels‐Alder Cycloaddition and Productive Applications in Organic Synthesis

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