scholarly journals Bilirubin conjugates of human bile. The excretion of bilirubin as the acyl glycosides of aldobiouronic acid, pseudoaldobiouronic acid and hexuronosylhexuronic acid, with a branched-chain hexuronic acid as one of the components of hexuronosylhexuronide

1970 ◽  
Vol 119 (3) ◽  
pp. 411-435 ◽  
Author(s):  
Clive C. Kuenzle
Keyword(s):  
Acyl Radical ◽  
Hepatic Bile ◽  
Human Bile ◽  
Hexuronic Acid ◽  
Acyl Radicals ◽  
Branched Chain

Structure elucidations have been performed on the bilirubin conjugates isolated from human hepatic bile as the phenylazo derivatives. The major bilirubin conjugates are excreted, not as was formerly thought in the form of glucuronides, but as the acyl glycosides of aldobiouronic acid, pseudoaldobiouronic acid and hexuronosylhexuronic acid. The isolated aldobiouronides are proposed to have the structures of an acyl 6-O-hexopyranosyluronic acid-hexopyranoside, an acyl 4-O-hexofuranosyluronic acid-d-glucopyranoside, and an acyl 4-O-β-d-glucofuranosyluronic acid-d-glucopyranoside respectively, with the acyl radicals being those of the phenylazo derivative of bilirubin. The pseudoaldobiouronide is suggested to be the acyl 4-O-α-d-glucofuranosyl-β-d -glucopyranosiduronic acid, with the acyl radical being that of the phenylazo derivative of vinylneoxanthobilirubinic acid. The hexuronosylhexuronide presumably is the acyl 4-O-(3-C-hydroxymethylribofuranosyluronic acid)-β-d-glucopyranosiduronic acid, with the acyl radical being that of the phenylazo derivative of bilirubin. The 3-C-hydroxymethylriburonic acid, isolated as one of the components of the hexuronosylhexuronide, is the first natural branched-chain hexuronic acid to be detected, and the first branched-chain sugar ever detected in humans.

scholarly journals Structure revision of disaccharidic conjugates of bilirubin-IX α in human bile and identification of phenylazo derivatives B4, B5, and B6 as 2-, 3- and 4-O-acylglucuronides

1978 ◽  
Vol 175 (3) ◽  
pp. 1095-1101 ◽  
Author(s):  
F Compernolle
Keyword(s):  
Mass Spectrometry ◽  
Glucuronic Acid ◽  
Chain Structure ◽  
Positional Isomers ◽  
Human Bile ◽  
Hexuronic Acid ◽  
Structure Revision ◽  
Branched Chain ◽  
Trimethylsilyl Derivatives

Aniline azopigments B4, B5 and B6, derived from conjugates of bilirubin-IX alpha in human bile, and previously characterized as disaccharidic esters [Kuenzle (1970) Biochem. J. 119, 387-394 and 411-435], were analysed by using t.l.c. and mass spectrometry. The compounds were identified as partially separated mixtures of 2-, 3- and 4-O-acylglucuronide positional isomers. The 1-O-acylglucuronide was not detected in the mixtures and was the only compound hydrolysed with beta-glucuronidase. Further scrutiny of structural assignments made by Kuenzle [(1970) Biochem. J. 119, 411-435] led to identification of the lactone and hexuronic acid derivatives that were obtained from azopigment B5 along with glucuronolactone and glucuronic acid. A branched-chain structure, i.e. 3-C-hydroxy-methyl-D-riburonic acid, was assigned previously, but the derivatives have now been identified as various incompletely silylated forms of glucuronolactone and glucuronic acid. Several trimethylsilyl derivatives glucuronolactone were isolated and characterized by n.m.r. and mass spectrometry.

Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage–Independent Activation of Strong C–O Bonds

2018 ◽  
Author(s):  
Erin Stache ◽  
Alyssa B. Ertel ◽  
Tomislav Rovis ◽  
Abigail G. Doyle
Keyword(s):  
Carboxylic Acids ◽  
Functional Groups ◽  
Single Step ◽  
Direct Access ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Synthetic Strategy ◽  
Acyl Radicals ◽  
Benzyl Radicals ◽  
Aliphatic Carboxylic Acids

Alcohols and carboxylic acids are ubiquitous functional groups found in organic molecules that could serve as radical precursors, but C–O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen centered nucleophile. We first show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H-atom trapping to afford the deoxygenated product. Using the same method, we demonstrate access to synthetically versatile acyl radicals which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge new C–O, C–N and C–C bonds in a single step.

scholarly journals Radical Carbonylative Synthesis of Heterocycles by Visible Light Photoredox Catalysis

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1054
Author(s):  
Xiao-Qiang Hu ◽  
Zi-Kui Liu ◽  
Wen-Jing Xiao
Keyword(s):  
Visible Light ◽  
Efficient Synthesis ◽  
Acyl Radical ◽  
Acyl Chlorides ◽  
Aryl Radicals ◽  
Keto Acids ◽  
Acyl Radicals ◽  
Different Types ◽  
The Impact ◽  
Visible Light Photocatalytic

Visible light photocatalytic radical carbonylation has been established as a robust tool for the efficient synthesis of carbonyl-containing compounds. Acyl radicals serve as the key intermediates in these useful transformations and can be generated from the addition of alkyl or aryl radicals to carbon monoxide (CO) or various acyl radical precursors such as aldehydes, carboxylic acids, anhydrides, acyl chlorides or α-keto acids. In this review, we aim to summarize the impact of visible light-induced acyl radical carbonylation reactions on the synthesis of oxygen and nitrogen heterocycles. The discussion is mainly categorized based on different types of acyl radical precursors.

Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage–Independent Activation of Strong C–O Bonds

2018 ◽  
Author(s):  
Erin Stache ◽  
Alyssa B. Ertel ◽  
Tomislav Rovis ◽  
Abigail G. Doyle
Keyword(s):  
Carboxylic Acids ◽  
Functional Groups ◽  
Single Step ◽  
Direct Access ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Synthetic Strategy ◽  
Acyl Radicals ◽  
Benzyl Radicals ◽  
Aliphatic Carboxylic Acids

Alcohols and carboxylic acids are ubiquitous functional groups found in organic molecules that could serve as radical precursors, but C–O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen centered nucleophile. We first show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H-atom trapping to afford the deoxygenated product. Using the same method, we demonstrate access to synthetically versatile acyl radicals which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge new C–O, C–N and C–C bonds in a single step.

Synthetic and Computational Studies of Acyl Radical Cyclizations with β-Alkoxyacrylates: Formal Synthesis of (±)-Longianone

2011 ◽  
Vol 64 (4) ◽  
pp. 409 ◽  
Author(s):  
Heather M. Aitken ◽  
Carl H. Schiesser ◽  
Christopher D. Donner
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Radical Cyclizations ◽  
Computational Studies ◽  
Fungal Metabolite ◽  
Acyl Radical ◽  
Functional Theory ◽  
Formal Synthesis ◽  
Acyl Radicals ◽  
Insight Into

An investigation into the cyclization of acyl radicals with mono- and disubstituted β-alkoxyacrylates is described. Ether-tethered acyl radicals, generated directly from the corresponding aldehyde, undergo cyclization to form dioxaspiro heterocyclic systems including 1,7-dioxaspiro[4,4]nonane-4,8-dione and 1,8-dioxaspiro[5,4]decane-5,9-dione. This strategy is applied to a concise formal synthesis of the fungal metabolite longianone. Density functional theory calculations provide insight into the chemistry of the acyl radicals in this study.

Recent Advances on Acyl Radical Enabled Reactions between Aldehydes and Alkenes

2021 ◽  
Author(s):  
Yilin Liu ◽  
Yuejun Ouyang ◽  
Hongxing Zheng ◽  
Hongxin Liu ◽  
Wenting Wei
Keyword(s):  
Hydrogen Atom ◽  
Acyl Radical ◽  
Recent Advances ◽  
Acyl Radicals

Radical-mediated functionalization of alkenes has been emerging as an elegant and straightforward protocol to increase molecule complexity. Moreover, the abstraction of a hydrogen atom from aldehydes to afford acyl radicals...

scholarly journals Bilirubin conjugates in bile of man, rat and dog. Semi-quantitative analysis of bile composition by thin-layer chromatography

1976 ◽  
Vol 155 (2) ◽  
pp. 365-373 ◽  
Author(s):  
B A. Noir
Keyword(s):  
Gall Bladder ◽  
Glucuronic Acid ◽  
Bile Pigments ◽  
Human Bile ◽  
Bile Composition ◽  
Hexuronic Acid ◽  
Normal Rat ◽  
Phenol Water ◽  
Layer Chromatography ◽  
Rat Bile

1. Conjugated bile pigments, separated in two fractions by semi-quantitative t.l.c. performed on silicic acid with phenol/water as the developing solvent, were treated with diazotized ethyl anthranilate. Resulting dipyrrylazo derivatives were analysed by quantitative t.l.c. 2. The tentative structure elucidation of tetrapyrrolic bilirubin conjugates and semi-quantitative evaluation of rat bile, post-obstructive human bile and dog bile composition is presented. 3. Homogeneous and mixed hexuronic acid diesters of bilirubin containing glucuronic acid constitute 51% of the total conjugates in normal rat bile, 45% of those in human post-obstructive bile and 38% of those in obstructed rat biles. 4. Monoconjugated bilirubin amounts to 33% of total conjugated bile pigments in normal rat bile, and 17 and 14% in post-obstructive hepatic human bile and gall-bladder bile of dog respectively. After loading with unconjugated bilirubin a greater amount of monoconjugates (56%) occur in the rat bile, whereas bilirubin diglucuronide excretion is decreased (34%). 5. In gall-bladder bile of normal dog, 40% of glucose-containing diconjugates, 32% of homogeneous and/or mixed hexuronic acid (mainly glucuronic acid) diesters of bilirubin and 14% of xylose-containing diconjugates are estimated. 6. Increased amounts of bilirubin conjugates, including some with unidentified uronic acid groups, were observed in cholestatic rat biles and quantities of conjugates with glucuronic acid were decreased.

Kinetic and Spectroscopic Studies on Acyl Radicals in Solution by Time-Resolved Infrared Spectroscopy

1995 ◽  
Vol 48 (2) ◽  
pp. 363 ◽  
Author(s):  
CE Brown ◽  
AG Neville ◽  
DM Rayner ◽  
KU Ingold ◽  
J Lusztyk
Keyword(s):  
Infrared Spectroscopy ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Spectroscopic Studies ◽  
Kinetic Properties ◽  
Acyl Radical ◽  
Time Resolved ◽  
Acyl Radicals ◽  
Time Resolved Infrared Spectroscopy

A number of acyl radicals, RĊ=O, have been generated in hexane or di -t-butyl peroxide as solvent at room temperature by 308 nm laser flash photolysis, and their spectroscopic and kinetic properties have been examined by time-resolved infrared spectroscopy. The C=O stretching frequencies for the RĊ=O radicals are found to be higher than those of the corresponding aldehydes, RCHO, by between 108 and 128 cm-1, an effect attributed to a higher C=O bond order in the radicals. For the RĊ=O radicals some typical values of vC =O are: CH3Ċ=O, 1864 cm-1; (CH3)3CĊ=O, 1848 cm-1; and C6H5Ċ=O, 1828 cm-1, while the corresponding acylperoxyl radicals, RC(O)OO, formed by reaction with oxygen have vC =O values of 1838, 1840 and 1820 cm-1, respectively. The acyl radicals exhibit a reactivity towards a variety of substrates that is roughly comparable to that of simple alkyl radicals. For reactions of the benzoyl radical some typical rate constants/M-1 s-1 are: CCl4, 6.0x104; C6H5SH, 4.8×107; CCl3Br, 2.2×108; Tempo, 1.1×109; and oxygen, 1.8×109. Alkanoyl radicals have a rather similar reactivity to benzoyl. The propanoyl radical reacts with tributyltin deuteride with a rate constant of 3×105 M-1s-1. The hex-5-enoyl radical undergoes a 5-exo-trig cyclization to form the 2-oxocyclopentylmethyl radical with a rate constant of 2.2×105 s-1, a value which is almost identical to that for cyclization of the hex-5-enyl radical. It is hoped that our kinetic data will prove useful in the planning of organic synthetic strategies which involve acyl radical chemistry.

Photoredox-catalyzed indirect acyl radical generation from thioesters

2018 ◽  
Vol 5 (22) ◽  
pp. 3267-3298 ◽  
Author(s):  
Alexander R. Norman ◽  
Martina N. Yousif ◽  
Christopher S. P. McErlean
Keyword(s):  
Acyl Radical ◽  
Acyl Radicals ◽  
Radical Generation

A photoredox-catalyzed method for the indirect generation of acyl radicals from stable thioesters is described.

scholarly journals Acyl Radical Chemistry via Visible-Light Photoredox Catalysis

Synthesis ◽  
2018 ◽  
Vol 51 (02) ◽  
pp. 303-333 ◽  
Author(s):  
Ming-Yu Ngai ◽  
Arghya Banerjee ◽  
Zhen Lei
Keyword(s):  
Visible Light ◽  
Carboxylic Acids ◽  
Easy Access ◽  
Hypervalent Iodine ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Diverse Range ◽  
Acyl Chlorides ◽  
Keto Acids ◽  
Acyl Radicals

Visible-light photoredox catalysis enables easy access to acyl radicals under mild reaction conditions. Reactive acyl radicals, generated from various acyl precursors such as aldehydes, α-keto acids, carboxylic acids, anhydrides, acyl thioesters, acyl chlorides, or acyl silanes, can undergo a diverse range of synthetically useful transformations, which were previously difficult or inaccessible. This review summarizes the recent progress on visible-light-driven acyl radical generation using transition-metal photoredox catalysts, metallaphotocatalysts, hypervalent iodine catalysts or organic photocatalysts.1 Introduction2 The Scope of This Review3 Aldehydes as a Source of Acyl Radicals4 α-Keto Acids as a Source of Acyl Radicals5 Carboxylic Acids as a Source of Acyl Radicals6 Anhydrides as a Source of Acyl Radicals7 Acyl Thioesters as a Source of Acyl Radicals8 Acyl Chlorides as a Source of Acyl Radicals9 Acyl Silanes as a Source of Acyl Radicals10 Conclusions and Future Outlook

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