OXIDATIVE REMOVAL OF <i>N</i>-(<i>p</i>-METHOXYBENZYL) GROUP ON DIKETOPIPERAZINE SKELETON WITH CERIC AMMONIUM NITRATE

Yoshimura, Juji; Yamaura, Masanori; Suzuki, Tateyuki; Hashimoto, H.

doi:10.1246/cl.1983.1001

Cited by 63 publications

(20 citation statements)

References 8 publications

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“…Condensation of aldehyde with t-butyl diethylphosphonoacetate followed by 1,4-addition of p-methoxybenzyl amine gave b-amino ester 23 as a mixture of diastereomers. Protection of secondary amine in 23 with Boc group, removal pmethoxybenzyl group under oxidative conditions, 12 and hydrolysis of the t-butyl ester furnished the desired bamino acid 24.…”

Section: Chemistrymentioning

confidence: 99%

Conformationally restricted analogs of deoxynegamycin

Raju

Anandan

et al. 2004

Bioorganic & Medicinal Chemistry Letters

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Section: Chemistrymentioning

confidence: 99%

Conformationally restricted analogs of deoxynegamycin

Raju

Anandan

et al. 2004

Bioorganic & Medicinal Chemistry Letters

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“…Next, oxidative removal [28] of the chiral auxiliary was investigated. Treatment of N-substituted 5-methyltetramate 12 a with cerium(IV) ammonium nitrate (CAN; 5.0 equiv) in a mixed solvent system (MeCN/H 2 O, 3:1, v/v, RT, 30 min) smoothly afforded the desired methyl (R)-5-methyltetramate (2 a) as white crystals.…”

Section: Resultsmentioning

confidence: 99%

A Flexible Asymmetric Approach to Methyl 5‐Alkyltetramates and Its Application in the Synthesis of Cytotoxic Marine Natural Product Belamide A

Lan

Wang

et al. 2010

Chemistry A European J

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By using a methyl tetramate derivative (R)- or (S)-9 as a novel chiral building block, a direct, flexible, and highly enantioselective approach to methyl (R)- or (S)-5-alkyltetramates (2) is disclosed. Among the synthesized methyl 5-alkyltetramates 2, methyl 5-methyltetramate (2 a) is found in cytotoxic mirabimide E (4) and dysideapyrrolidone (5), and methyl 5-benzyltetramate (2 g) is a substructure in the potent antineoplastic dolastatin 15 (3). On the basis of this method, the first asymmetric synthesis of the antimitotic tetrapeptide belamide A (7) has been achieved in seven steps from (S)-9, with an overall yield of 23.8 %. Not only have the structure and absolute configuration of (+)-belamide A (7) been confirmed, but also the solvent used for recording the (13) C NMR spectrum, the (13) C NMR spectrum data correlation, and optical rotation data of natural belamide A (7) have been revised.

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“…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.

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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...

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OXIDATIVE REMOVAL OF N-(p-METHOXYBENZYL) GROUP ON DIKETOPIPERAZINE SKELETON WITH CERIC AMMONIUM NITRATE

Abstract: N-(p-Methoxybenzyl) groups in some diketopiperazine derivatives were proved to be readily and efficiently removed with ceric ammonium nitrate in acetonitrile-water under mild conditions, where N-benzyl , methoxyl in the aminal structure, and isolated vinyl groups remained unchanged.

Cited by 63 publications

References 8 publications

Conformationally restricted analogs of deoxynegamycin

Conformationally restricted analogs of deoxynegamycin

A Flexible Asymmetric Approach to Methyl 5‐Alkyltetramates and Its Application in the Synthesis of Cytotoxic Marine Natural Product Belamide A

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

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OXIDATIVE REMOVAL OF N-(p-METHOXYBENZYL) GROUP ON DIKETOPIPERAZINE SKELETON WITH CERIC AMMONIUM NITRATE

Abstract: N-(p-Methoxybenzyl) groups in some diketopiperazine derivatives were proved to be readily and efficiently removed with ceric ammonium nitrate in acetonitrile-water under mild conditions, where N-benzyl , methoxyl in the aminal structure, and isolated vinyl groups remained unchanged.

Cited by 63 publications

References 8 publications

Conformationally restricted analogs of deoxynegamycin

Conformationally restricted analogs of deoxynegamycin

A Flexible Asymmetric Approach to Methyl 5‐Alkyltetramates and Its Application in the Synthesis of Cytotoxic Marine Natural Product Belamide A

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

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