Stereocontrolled total synthesis of (.+-.)- and (+)-bicyclomycin

Williams, Robert M.; Armstrong, Robert W.; Dung, Jen Sen

doi:10.1021/ja00297a035

Cited by 38 publications

(16 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Ther equired alkoxyamine 30 was obtained in three steps from known dichloroacetamide 27 [7a] through oxygenative cyclization to give 28 under basic conditions,C rabbe homologation [23] to give 29, and enolate oxygenation under internal quench conditions. [27] In conclusion, we have developed ac onceptually new approach to diverse bridged diketopiperazines by introducing an ovel class of amino acid derived alkoxyamines as radical surrogates and taking advantage of an inherently atomeconomic cyclization that makes use of the PRE. [25] Reductive removal of the tetramethylpiperidinyl unit with zinc in acetic acid afforded allylic alcohol 32.I ti s important to mention that the sensitive hemiaminal functionality at the bridgehead position survived the acidic and reductive conditions.Areductive transposition of the internal double bond to the exo position under the conditions developed by Movassaghi and Ahmad [26] furnished Williams central intermediate 34 in 6s teps and 38 %o verall yield.…”

Section: Methodsmentioning

confidence: 99%

Synthesis of Bridged Diketopiperazines by Using the Persistent Radical Effect and a Formal Synthesis of Bicyclomycin

et al. 2015

View full text Add to dashboard Cite

show abstract

Section: Methodsmentioning

confidence: 99%

Synthesis of Bridged Diketopiperazines by Using the Persistent Radical Effect and a Formal Synthesis of Bicyclomycin

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Hydrogen peroxide-mediated oxidation of selenide 30 to selenoxide 31 was performed in an effort to induce syn -elimination of the selenoxide. 27 Although purification of selenoxide 31 was not conducted, the 1 H NMR spectrum of the crude product reveals a clean mixture of two selenoxide diastereomers. Selenoxide 31 was suspended in toluene and gradually warmed to refluxing temperature over the course of 24 h. In addition to the isolation of 4- epi -papyracillic acid B ( 32 ), a second diastereomer was isolated as part of a 1:1 mixture.…”

Section: Resultsmentioning

confidence: 99%

Syntheses of Papyracillic Acids: Application of the Tandem Chain Extension–Acylation Reaction

Mazzone

Zercher

2012

J. Org. Chem.

View full text Add to dashboard Cite

A synthetic approach to the papyracillic acid family of natural products has been developed. The spiroacetal core is rapidly assembled through an unprecedented zinc carbenoid-mediated tandem chain extension-acylation reaction. Subsequent functional group manipulation provided access to papyracillic acid B and 4-epi-papyracillic acid C. The successful preparation of these molecules resulted in the clarification of structural assignments of members of this family of natural products.

show abstract

“…50,51) While these conditions were found to effect deprotection on the simple, unsubstituted compound 54, the presence of the electron-rich indoxyl apparently reacted much faster with the oxidizing reagent than did the N-para-methoxybenzyl group. Additional attempts to remove the N-para-methoxybenzyl protecting group by dissolving metal reduction; catalytic hydrogenation; acidic solvolysis; boron tribromide; boron trichloride; 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) oxidation and photooxidation all met with complete failure to provide even a trace of brevianamide B.…”

Section: )mentioning

confidence: 99%

Total Synthesis and Biosynthesis of the Paraherquamides: An Intriguing Story of the Biological Diels–Alder Construction

Williams

2002

Chem. Pharm. Bull.

View full text Add to dashboard Cite

The paraherquamides constitute an unusual family of prenylated indole alkaloids that are secondary metabolites produced by Penicillium sp. and Aspergillus sp. fungi. This review will cover both the biosynthesis as well as the chemical synthesis of this family of natural products. Particular emphasis will be placed on the provocative hypothesis that the core bicyclo[2.2.2]diazaoctan ring system, which is common to this entire family, is formed by a biological DielsAlder reaction.Despite its widespread use in synthetic organic chemistry, the Diels-Alder cycloaddition reaction does not occur frequently in nature. 1,2) There are just a few reports in the literature claiming the identification of an enzyme that catalyzes this most ubiquitous synthetic ring-forming reaction. [3][4][5][6] A possible explanation for this is that, enzymes generally catalyze reactions by stabilizing the structure and charge of the developing transition state. For most reactions subject to this stratagem of catalysis, both the starting substrate and the product differ significantly with respect to structure from the transition state; it is this fundamental difference that allows for turnover; i.e., both the product and the starting substrate must bind to the enzyme less tightly than the transition state structure. In the Diels-Alder reaction, the transition state is highly ordered and closely resembles the structure of the product (see Fig. 1, below). In other words, an enzyme that was designed to stabilize the transition state structure for this reaction would be expected to be inhibited by the product (via tight binding) and turnover (thus catalysis) would be precluded. It is from within the excitement of this fundamental question, that this review will hold as a guiding light.The only examples of protein-catalyzed Diels-Alder reactions are those of catalytic antibodies that have recently been shown to catalyze the intermolecular [4ϩ2] cycloaddition reaction.7-9) In these cases, the initial Diels-Alder adducts were high-energy substances that significantly change their structure or conformation after the initial cyclocondensation and were subsequently released from the antibody CDR (allowing for turnover). In addition, ribozymes have been reported to catalyze the Diels-Alder reaction and findings in this area have been reviewed. 10) The Penicillium sp. that produces the brevianamides/paraherquamides may be a rare, but vitally important example of the existence of DielsAlderases. It is further significant to note in the context of the catalytic antibody stratagem that, the brevianamide DielsAlder adducts (which are proposed to be the brevianamides themselves) are very rigid substances; therefore, a significant change in conformation or structure is either impossible or highly unlikely. Elucidation of the mechanism for turnover in the purported paraherquamide and brevianamide [4ϩ2] cycloaddition reaction should be an extremely interesting and significant finding.In order to do proper justice to the history of the biosynthetic Diels-Alder p...

show abstract

Stereocontrolled total synthesis of (.+-.)- and (+)-bicyclomycin

Cited by 38 publications

References 1 publication

Synthesis of Bridged Diketopiperazines by Using the Persistent Radical Effect and a Formal Synthesis of Bicyclomycin

Synthesis of Bridged Diketopiperazines by Using the Persistent Radical Effect and a Formal Synthesis of Bicyclomycin

Syntheses of Papyracillic Acids: Application of the Tandem Chain Extension–Acylation Reaction

Total Synthesis and Biosynthesis of the Paraherquamides: An Intriguing Story of the Biological Diels–Alder Construction

Contact Info

Product

Resources

About

Stereocontrolled total synthesis of (.+-.)- and (+)-bicyclomycin

Cited by 38 publications

References 1 publication

Synthesis of Bridged Diketopiperazines by Using the Persistent Radical Effect and a Formal Synthesis of Bicyclomycin

Synthesis of Bridged Diketopiperazines by Using the Persistent Radical Effect and a Formal Synthesis of Bicyclomycin

Syntheses of Papyracillic Acids: Application of the Tandem Chain Extension–Acylation Reaction

Total Synthesis and Biosynthesis of the Paraherquamides: An Intriguing Story of the Biological Diels&ndash;Alder Construction

Contact Info

Product

Resources

About

Total Synthesis and Biosynthesis of the Paraherquamides: An Intriguing Story of the Biological Diels–Alder Construction