scholarly journals Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

2020 ◽  
Vol 16 ◽  
pp. 1-8 ◽  
Author(s):  
Renata Kaczmarek ◽  
Dariusz Korczyński ◽  
James R Green ◽  
Roman Dembinski
Keyword(s):  
Bond Formation ◽  
Side Chain ◽  
Nicholas Reaction ◽  
Propargyl Ether ◽  
Dicobalt Hexacarbonyl

Dicobalt hexacarbonyl nucleoside complexes of propargyl ether or esters of 5-substituted uridines react with diverse C-nucleophiles. Synthetic outcomes confirmed that the Nicholas reaction can be carried out in a nucleoside presence, leading to a divergent synthesis of novel metallo-nucleosides enriched with alkene, arene, arylketo, and heterocyclic functions, in the deoxy and ribo series.

Peptide Modifications: Versatile Tools in Peptide and Natural Product Syntheses

Synlett ◽  
2019 ◽  
Vol 30 (11) ◽  
pp. 1289-1302 ◽  
Author(s):  
Phil Servatius ◽  
Lukas Junk ◽  
Uli Kazmaier
Keyword(s):  
Amino Acids ◽  
Natural Product ◽  
Bond Activation ◽  
Bond Formation ◽  
Side Chain ◽  
Peptide Backbone ◽  
Claisen Rearrangements ◽  
The Past ◽  
Allylic Alkylations ◽  
Peptide Modifications

Peptide modifications via C–C bond formation have emerged as valuable tools for the preparation and alteration of non-proteinogenic amino acids and the corresponding peptides. Modification of glycine subunits in peptides allows for the incorporation of unusual side chains, often in a highly stereoselective manner, orchestrated by the chiral peptide backbone. Moreover, modifications of peptides are not limited to the peptidic backbone. Many side-chain modifications, not only by variation of existing functional groups, but also by C–H functionalization, have been developed over the past decade. This account highlights the synthetic contributions made by our group and others to the field of peptide modifications and their application in natural product syntheses.1 Introduction2 Peptide Backbone Modifications via Peptide Enolates2.1 Chelate Enolate Claisen Rearrangements2.2 Allylic Alkylations2.3 Miscellaneous Modifications3 Side-Chain Modifications3.1 C–H Activation3.1.1 Functionalization via Csp3–H Bond Activation3.2.2 Functionalization via Csp2–H Bond Activation3.2 On Peptide Tryptophan Syntheses4 Conclusion

Critical Review of Biotransformational Studies on Steroids by Using Culture of Cunninghamella blakesleeana

2021 ◽  
Vol 18 ◽  
Author(s):  
Azizuddin ◽  
Muhammad Iqbal ◽  
Syed Ghulam Musharraf
Keyword(s):  
Double Bond ◽  
Critical Review ◽  
Structural Modification ◽  
Bond Formation ◽  
Environmentally Friendly ◽  
Side Chain ◽  
Synthetic Compounds ◽  
Efficient Approach ◽  
Cunninghamella Blakesleeana ◽  
Different Strains

: For several decades, biotransformational studies on steroidal compounds have gained a lot of attention because it is an efficient approach for the structural modification of complicated natural or synthetic compounds with high regio-, chemo- and stereoselectivity at environmentally friendly conditions. This review summarizes the use of different strains of Cunninghamella blakesleeana for the biotransformation of sixteen steroids 1-16 into a variety of transformed products. The transformed products may be important as a drug or precursor for the production of important pharmaceuticals. The types of reactions performed by C. blakesleeana include hydroxylation, epoxidation, reduction, demethylation, oxidation, glycosidation, double bond formation, side-chain degradation, isomerisation and opening of an isoxazol ring, which would be difficult to produce by traditional synthesis.

Efficient Synthesis of O-tert-Propargylic Oximes via Nicholas Reaction

Synthesis ◽  
2020 ◽  
Vol 52 (22) ◽  
pp. 3461-3465
Author(s):  
Itaru Nakamura ◽  
Keigo Shiga ◽  
Mao Suzuki ◽  
Masahiro Terada
Keyword(s):  
Ammonium Nitrate ◽  
Efficient Synthesis ◽  
Propargylic Alcohols ◽  
Cyclic Nitrones ◽  
Acidic Catalysts ◽  
Nicholas Reaction ◽  
High Yields ◽  
Dicobalt Hexacarbonyl ◽  
Cerium Iv Ammonium Nitrate

A synthetic protocol to access O-tert-propargylic oximes derived from tertiary propargylic alcohols was established via Nicholas reaction. Thus, BF3·OEt2-mediated reaction between the dicobalt hexacarbonyl complex of tert-propargylic alcohols and p-nitrobenzaldoxime followed by decomplexation with cerium(IV) ammonium nitrate afforded the corresponding O-tert-propargylic oximes in good to high yields. The obtained O-tert-propargylic oximes were effectively converted into heterocycles, such as four-membered cyclic nitrones, oxazepines, and isoxazolines, by using π-Lewis acidic catalysts.

scholarly journals The Position 68(E11) Side Chain in Myoglobin Regulates Ligand Capture, Bond Formation with Heme Iron, and Internal Movement into the Xenon Cavities

2005 ◽  
Vol 280 (46) ◽  
pp. 38740-38755 ◽  
Author(s):  
David Dantsker ◽  
Camille Roche ◽  
Uri Samuni ◽  
George Blouin ◽  
John S. Olson ◽  
...  
Keyword(s):  
Bond Formation ◽  
Heme Iron ◽  
Side Chain

scholarly journals Microbiological degradation of bile acids. Nitrogenous hexahydroindane derivatives formed from cholic acid by Streptomyces rubescens

1976 ◽  
Vol 160 (3) ◽  
pp. 745-755 ◽  
Author(s):  
S Hayakawa ◽  
S Hashimoto ◽  
T Onaka
Keyword(s):  
Cholic Acid ◽  
Bond Formation ◽  
Valeric Acid ◽  
Amide Bond ◽  
Side Chain ◽  
Mechanism Of Formation ◽  
Partial Synthesis ◽  
Degradative Pathway ◽  
Amide Bond Formation ◽  
New Compounds

The metabolism of cholic acid (I) by Streptomyces rubescens was investigated. This organism effected ring A cleavage, side-chain shortening and amide bond formation and gave the following metabolites: (4R)-4-[4α-(2-carboxyethyl)-3aα-hexahydro-7aβ-methyl-5-oxoindan-1 β-yl]valeric acid (IIa) and its mono-amide (valeramide) (IIb); and 2,3,4,6, 6aβ,7,8,9,9aα,9bβ-decahydro-6aβ-methyl-1H-cyclopenta[f]quinoline-3,7-dione(IIIe)and its homologues with the β-oriented side chains, valeric acid, valeramide, butanone and propionic acid, in the place of the oxo group at C-7, i.e.compounds (IIIa), (IIIb), (IIIc) and (IIId) respectively. All the nitrogenous metabolites were new compounds, and their structures were established by partial synthesis except for the metabolite (IIIc). The mechanism of formation of these metabolites is considered. A degradative pathway of cholic acid (I) into the metabolites is also tentatively proposed.

scholarly journals P450 monooxygenase ComJ catalyses side chain phenolic cross-coupling during complestatin biosynthesis

RSC Advances ◽  
2017 ◽  
Vol 7 (56) ◽  
pp. 35376-35384 ◽  
Author(s):  
Aurelio Mollo ◽  
A. Nikolai von Krusenstiern ◽  
Joshua A. Bulos ◽  
Veronika Ulrich ◽  
Karin S. Åkerfeldt ◽  
...  
Keyword(s):  
High Efficiency ◽  
Bond Formation ◽  
Cross Coupling ◽  
Side Chain ◽  
P450 Monooxygenase ◽  
Peptide Substrates ◽  
Ether Bond ◽  
Biaryl Ether

P450 monooxygenase enzyme ComJ catalyzed biaryl ether bond formation with high efficiency and low stereoselectivity on selected complestatin-like peptide substrates.

Kinetic studies on cyclopalladation in palladium(II) complexes containing an indole moiety

2014 ◽  
Vol 86 (2) ◽  
pp. 151-161 ◽  
Author(s):  
Satoshi Iwatsuki ◽  
Takuya Suzuki ◽  
Syogo Tanooka ◽  
Tatsuo Yajima ◽  
Yuichi Shimazaki
Keyword(s):  
Bond Formation ◽  
Kinetic Studies ◽  
Catalytic Reactions ◽  
Biological Molecules ◽  
Side Chain ◽  
Formation Mechanisms ◽  
Indole Derivatives ◽  
Reaction Intermediates ◽  
Pd Catalysts ◽  
Amino Acid Tryptophan

Abstract Various Pd–C complexes have been developed to date, affording deep insights into the reaction intermediates in useful catalytic reactions in organic syntheses. Cyclopalladation is one of the most famous Pd–C bond formation reactions to generate the palladacycles. Indole is an electron-rich aromatic ring involved in the side chain of an essential amino acid, tryptophan (Trp), and Trp and its derivatives are important in biological systems, such as electron transfer in protein, cofactors for conversion of biological molecules and so on. Pd catalysts are also useful for syntheses of such indole derivatives, and the mechanisms are considered to be through the Pd–C intermediates. However, the detailed properties and formation mechanisms of Pd–indole species are still unclear. With these points in mind, we focus on Pd(II)–indole-C2 carbon bond formations using various Pd(II) complexes having an indole moiety, especially on the recent studies on the kinetic analyses for these cyclopalladation reactions and their detailed mechanisms.

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