Substitution, Oxidation and Group Participation in the Bromination of Indoles

Lawson, William B.; Patchornik, A.; Witkop, Bernhard

doi:10.1021/ja01507a031

Cited by 65 publications

(34 citation statements)

References 4 publications

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“…Since the ester moiety of 8 is located on the endo face of this concave skeleton, we thought if the ester could participate in this reaction, the intramolecular nucleophilic attack of the carbonyl oxygen of ester moiety at the C3 position of the intermediate 20 would give the desired spirolactone product. However, established methods such as the use of NBS,– t ‐BuBr/DMSO, NaI/H 2 O 2 , Ms 2 O/DMSO, (COCl) 2 /DMSO, or TTN, gave no reaction or low yield. Pleasingly, after extensive experimentation, we found that treatment of 8 with NCS in t ‐BuOH/H 2 O provided lactone 7 as a single diastereoisomer.…”

Section: Figurementioning

confidence: 99%

A Ten‐Step Total Synthesis of Speradine C

et al. 2019

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The first total synthesis of speradine Ch as been achieved in only ten steps from ac ommercially available 4bromoindole.Salient features of the work are the formation of four rings through three cyclizations,n amely ab ioinspired [3+ +2] annulation to form the C/D rings,a nN CS-mediated oxidation to construct the Ering, and aR u-catalyzed ketohydroxylation to assemble the Fring. This work highlights how strategic ring constructions can streamline the synthesis of polycyclic compounds. Scheme 1. Retrosynthetic analysis of speradine C.Scheme 2. Synthesis of tetracycle 9.THF = tetrahydrofuran, DMF = N,N-dimethylformamide, Tf = trifluoromethanesulfonyl, LiHMDS = lithium hexamethyldisilazide.Scheme 3. Proposed mechanism for the formation of 9a-c.

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Section: Figurementioning

confidence: 99%

A Ten‐Step Total Synthesis of Speradine C

et al. 2019

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“…Tyrosine and histidine are not modified with this reagent. This reaction is analogous to the oxidation with N-bromosuccinimide (NBS) (Lawson et al, 1960), with respect to the formation of an iminolactone (Scheme 9). Although the complexities of the process of this modification and its product(s) have prevented chemical analyses from clarifying the mechanism in proteins, it seems to be worth reexamining the reaction taking advantage of the present MS for the possible usages of this and the other similar oxidation methods (Spande et al ., 1970).…”

Section: Oxidation and Chemical Cleavagementioning

confidence: 99%

Chemistry in Proteomics: An Interplay between Classical Methods in Chemical Modification of Proteins and Mass Spectrometry at the Cutting Edge

Nakazawa

2006

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This review deals with chemical approaches that facilitate proteomics research. The methods include chemical cleavage of peptide bonds, stepwise degradation of proteins, and site-specific modification enabling the discrimination between functional groups. These reactions could enhance the efficacy of mass spectrometry (MS) for identification, quantification, and sequencing of peptides and proteins. Particular stress is laid on the effect of each modification on mass spectra mainly with respect to the enhancement of peak intensities, the clarity of spectra, and the suppression of ambiguity in peak assignment. Chemical modifications targeting the terminal free amino and carboxyl groups are reviewed, because the charge or isotopic tagging on N-and C-termini has proved effective to identify a protein based on the terminal amino acid sequencing with tandem MS in combination with database searching. Such a tag that is designed to provide a peak with a characteristic sensitivity or pattern could corroborate the implication of mass spectra and facilitate the de novo protein sequencing of mature proteins, which are often subjected to post-translational modifications.

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“…However, neither treatment had any affect on the mitogenicity. Furthermore, since NBS treatment degraded cystine, methionine, tyrosine, histidine, or lysine residues (15), it can be considered that these residues are not concerned with mitogenicity.…”

Section: Characterization Of Active Site(s) In the Mioogenicity Of Vementioning

confidence: 99%

Requirement of Anionic Groups for the Mitogenicity of a Fungal Mitogen, Vesiculogen

Ohno

Suzuki

Miyazaki

et al. 1984

Microbiology and Immunology

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Active site(s) of a B‐cell mitogen, vesiculogen, was investigated by means of chemical and enzymic modifications. Vesiculogen is a non‐dialyzable fraction of a hot water extract from a fungus, Peziza vesiculosa (Yadomae et al, Microbiol. Immunol. 23, 997 (1979)), and was composed of protein (~60%), carbohydrate (~30%), and a small amount of amino sugar, uronic acid, phosphate, and lipid. The mitogenicity was not affected by periodate oxidation, N‐acylation, defatting treatment, destruction of the three dimentional structure, protease digestion, nuclease digestion, N‐bromosuccinimide treatment, and β‐mercaptoethanol treatment. However, the mitogenicity was decreased by a modification of carboxyl groups, such as 1‐ethyl‐3(3‐dimethylamino propyl)‐carbodiimide or dicyclohexylcarbodiimide treatment. Vesiculogen contains a large amount of acidic amino acids. These results suggest that the mitogenicity of vesiculogen is due to the presence of anionic groups, such as aspartic acid and glutamic acid, and that the mitogenic substance is a novel, heat stable polyanionic B‐cell activator obtained from Ascomycotina.

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Substitution, Oxidation and Group Participation in the Bromination of Indoles

Cited by 65 publications

References 4 publications

A Ten‐Step Total Synthesis of Speradine C

A Ten‐Step Total Synthesis of Speradine C

Chemistry in Proteomics: An Interplay between Classical Methods in Chemical Modification of Proteins and Mass Spectrometry at the Cutting Edge

Requirement of Anionic Groups for the Mitogenicity of a Fungal Mitogen, Vesiculogen

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