Alternaric acid: formal synthesis and related studies

Slade, Michael; Johnson, Jeffrey S.

doi:10.3762/bjoc.9.19

Cited by 18 publications

(19 citation statements)

References 45 publications

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“…They devised two analogous strategies for the synthesis of Alternaric Acid; coupling (S)-2-methylbutanal 45 22 in one case and silylglyoxylate 63 in the other with vinyl and allyl Grignard 28 . In their first approach, reactions were proceeded in the presence of (-)-sparteine using vinyl Grignard 69 to yield coupling product 70 in 65% yield and >20:1 syn/anti aldol and 1.7:1 facial selectivity.…”

Section: Scheme 15mentioning

confidence: 99%

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Advances in Total Synthesis of Alternaric Acid: An Anti-Fungal and Phytotoxic Natural Product

Ahmad

Yousaf

Zahoor

et al. 2017

J. Chil. Chem. Soc.

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ABSTRACT:Alternaric acid is characterized as 1,4-diene, possessing (E)-1,2-disubstituted alkene known for nanomolar phytotoxic and antifungal activities. This article highlights the major synthetic approaches attempted towards the total synthesis of alternaric acid reported by three groups (Ichihara & coworkers, Trost & coworkers and Johnson and Slade) which involved novel pathways for the rapid construction of this functionalized natural molecule.

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Section: Scheme 15mentioning

confidence: 99%

“…Slade and Johnson exploited the role of silylglyoxylate for variety of synthetic activities which involved successful introduction of electrophilic and nucleophilic subunits on glycolic moiety to build a molecular complexity 28 .…”

Section: Synthesis By Slade and Johnsonmentioning

confidence: 99%

Advances in Total Synthesis of Alternaric Acid: An Anti-Fungal and Phytotoxic Natural Product

Ahmad

Yousaf

Zahoor

et al. 2017

J. Chil. Chem. Soc.

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“…Va rious aromatic imines (Scheme 3, formation of 5a,d,g,h) could be used successfully in this reaction in good to excellent diastereomeric ratios. One approach to further increase the complexity of the formed linear products 5 would be to start from allylic alcohols syn-E-4d,e possessing an extra stereogenic center through the Felkin-Anh-Eisenstein model for the addition of metalated enol carbamate 3 to chiral aldehydes (R 3 = CH-(Me)Ph for syn-E-4d,and R 3 = CH(Me)-CMe(SCH 2 CH 2 ) 2 [28] for syn-E-4e)a su nique diastereoisomers.W hen these two substrates were treated with BuLi and then imine,t he stereodefined tetrads 5j,k were obtained in moderate yields but with good diastereoselectivities (Scheme 3). Having in hand an easy approach to prepare stereodefined fully substituted ketone lithium enolate 1 as single isomer from allylic alcohols through the carbamoyl transfer, we then decided to further improve the efficiency of our approach by directly transforming enol carbamate 2 into the Mannich products 5 in asingle-pot operation.…”

Section: Angewandte Chemiementioning

confidence: 99%

“…[28] Therefore,the Mukaiyama aldol reaction was tested by addition of one equivalent of TiCl 4 at low temperature with various aldehydes and to our delight the reaction proceeded smoothly to give the desired aldol products 7a-f with the formation of aquaternary stereocenter in moderate yields but outstanding diastereoisomeric ratios (Scheme 6). [29,30] Thec onfiguration of the aldol products was determined by X-ray analyses of 7a, c (Supporting Information).…”

Section: Angewandte Chemiementioning

confidence: 99%

Stereoselective Formation of Fully Substituted Ketone Enolates

et al. 2016

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The application of stereochemically defined acyclic fully substituted enolates of ketones to the enantioselective synthesis of quaternary carbon stereocenters would be highly valuable.H erein, we describe an approach leading to the formation of several new stereogenic centers through ac ombined metalation-addition of acarbonyl-carbamoyl transfer to reveal in situ stereodefined a,a-disubstituted enolates of ketone as asingle stereoisomer.This approach could produce aseries of aldol and Mannich products from enol carbamate with excellent diastereomeric ratios.The carbonyl group is one of the most versatile and broadly utilized functional groups in organic synthesis.[1] Thes uccess of this widely employed starting material results from its multiple reactivities.Reactions proceed either at the electrophilic carbon or nucleophilic oxygen center of the carbonyl group,o ra lternatively at the adjacent CÀHp osition by removing an acidic hydrogen. In the latter case,anenolate for carbon-carbon and carbon-heteroatom bonds formation is generated. Taking into consideration the significance of enolates as valuable intermediates in asymmetric organic synthesis, [2] one can evaluate the consequence of developing efficient methods to the direct access of a,a-disubstituted metal enolates 1 as ar oute to the formation of challenging quaternary carbon stereocenters (Scheme 1, Path A). [3] Indeed, one structural element that invariably increases the difficulty of achemical synthesis is the presence of quaternary carbon stereocenters in the target molecule.[4] Thei mpediment to synthesis presented by such centers arises from the steric congestion imposed by the four attached carbons.I f such stereocenters could be prepared in asingle-pot operation through the formation of several CÀCb onds from common and easily accessible starting materials,i tw ould surely find numerous applications in organic synthesis. [5,6] However,t he generation of as tereodefined fully substituted enolate precursor as as ingle isomer in acyclic systems is not atrivial task, especially for ketone enolates,a nd therefore all the enolization reactions leading to stereodefined a,a-disubstituted enolates were restricted to esters and amides.F or instance, a,a-acyclic disubstituted esters require ap erfect conformational control for the abstraction of the a-hydrogen, [3] and this control can only be achieved by deprotonation of diastereomerically pure a,a-acyclic dialkylated amides, [7] enantiomerically pure a,a-acyclic dialkylated esters with chiral bases (Scheme 1, Path B), [8] or through conjugate additions.[9]As we have been involved over the last few years in the development of synthetic strategies leading to the creation of several carbon-carbon bonds in acyclicsystems and as inglepot operation, including the formation of quaternary carbon stereocenters, [5,10] we reported adirect access to the formation of a,a-disubstituted enolates of amides by carbocupration of ynamides followed by selective oxidation of the resulting alkenyl cuprates species (S...

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“…Additionally,t he fully substituted silyl enol ethers 6a-d previously prepared as as ingle stereoisomer by silylation of enolate 1 (Scheme 4) could also represent ideal candidates for the Mukaiyama aldol reaction giving access to b-hydroxy alcohols possessing aq uaternary stereocenter a to the carbonyl groups. [28] Therefore,the Mukaiyama aldol reaction was tested by addition of one equivalent of TiCl 4 at low temperature with various aldehydes and to our delight the reaction proceeded smoothly to give the desired aldol products 7a-f with the formation of aquaternary stereocenter in moderate yields but outstanding diastereoisomeric ratios (Scheme 6). [29,30] Thec onfiguration of the aldol products was determined by X-ray analyses of 7a, c (Supporting Information).…”

mentioning

confidence: 99%