scholarly journals Natural Product Studies on the Hamigerans

2021 ◽  
Author(s):  
◽  
Ethan Woolly
Keyword(s):  
Amino Acids ◽  
Methyl Ester ◽  
Natural Product ◽  
Structural Elucidation ◽  
The Other ◽  
Nitrogenous Compounds ◽  
New Compounds

<p>This study describes the NMR-directed isolation and structural elucidation of several new and semi-synthesised compounds. Carrying on from the previous examinations on the sponge Hamigera tarangaensis undertaken at VUW resulted in the isolation of an additional seven congeners to the hamigeran family. These included three debrominated analogues (37, 60, 62), an alternative methyl ester analogue (63) and a 4-brominated analogue (64). Two structures with novel functionality were also isolated, which were found in fractions previously not investigated, the nitrile containing hamigeran R (61) and the dimer hamigeran S (65). The isolation of these novel compounds led to the proposal of a biosynthesis from a reaction with hamigeran G (40) and ammonia, similar to the previous nitrogenous hamigerans biosynthesis with amino acids.   Semi-synthesis was undertaken to probe the biosynthesis of these and the other nitrogenous compounds. The results of this produced four new compounds: two imine intermediates, hamigeran G imine (66) and hamigeran B imine (70), a glycine derived hamigeran (68) and the hamigeran D epimer (69).</p>

scholarly journals Natural Product Studies on the Hamigerans

2021 ◽  
Author(s):  
◽  
Ethan Woolly
Keyword(s):  
Amino Acids ◽  
Methyl Ester ◽  
Natural Product ◽  
Structural Elucidation ◽  
The Other ◽  
Nitrogenous Compounds ◽  
New Compounds

<p>This study describes the NMR-directed isolation and structural elucidation of several new and semi-synthesised compounds. Carrying on from the previous examinations on the sponge Hamigera tarangaensis undertaken at VUW resulted in the isolation of an additional seven congeners to the hamigeran family. These included three debrominated analogues (37, 60, 62), an alternative methyl ester analogue (63) and a 4-brominated analogue (64). Two structures with novel functionality were also isolated, which were found in fractions previously not investigated, the nitrile containing hamigeran R (61) and the dimer hamigeran S (65). The isolation of these novel compounds led to the proposal of a biosynthesis from a reaction with hamigeran G (40) and ammonia, similar to the previous nitrogenous hamigerans biosynthesis with amino acids.   Semi-synthesis was undertaken to probe the biosynthesis of these and the other nitrogenous compounds. The results of this produced four new compounds: two imine intermediates, hamigeran G imine (66) and hamigeran B imine (70), a glycine derived hamigeran (68) and the hamigeran D epimer (69).</p>

THE OXIDATION OF ESTRONE-16-C14BY PEROXIDASE

1962 ◽  
Vol 40 (1) ◽  
pp. 459-469 ◽  
Author(s):  
P. H. Jellinck ◽  
Louise Irwin
Keyword(s):  
Amino Acids ◽  
Hydrogen Peroxide ◽  
Amino Acid ◽  
Serum Albumin ◽  
Oxidase Activity ◽  
Water Soluble ◽  
The Other ◽  
Aerobic Incubation ◽  
Nitrogenous Compounds ◽  
Initial Generation

Aerobic incubation of estrone-16-C14with peroxidase in the presence of serum albumin and other proteins resulted in the formation of water-soluble, ether-insoluble metabolites in high percentage yields. Similar products were formed when protein was replaced by cysteine or tryptophan but none of the other amino acids tested had any effect. The evidence points to an initial generation of hydrogen peroxide from these nitrogenous compounds by the enzyme acting as an aerobic oxidase, and the subsequent peroxidation of estrone to highly reactive products. These then combine with the protein or amino acid or else undergo alternative reactions. A strong chemical bond is formed with albumin and attempts to release the estrone metabolites from it were unsuccessful. Uterine homogenates from estrogen-treated rats showing high DPNH oxidase activity contained no "peroxidase" as measured by the formation of water-soluble products from estrone in the presence of protein.

LYTIC ENZYMES OF SORANGIUM SP.: A COMPARISON OF THE PROTEOLYTIC PROPERTIES OF THE α- AND β-LYTIC PROTEASES

1965 ◽  
Vol 43 (12) ◽  
pp. 1961-1970 ◽  
Author(s):  
D. R. Whitaker ◽  
C. Roy ◽  
C. S. Tsai ◽  
L. Jurášek
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Methyl Ester ◽  
Esterase Activity ◽  
The Other ◽  
Carboxyl Group ◽  
Lytic Enzymes ◽  
Amidase Activity ◽  
A Chain ◽  
Hydrolysis Of

The proteolytic properties of the α- and β-lytic proteases of a species of Sorangium were compared. Neither enzyme showed evidence of aminopeptidase, carboxypeptidase, or amidase activity in tests with a series of peptides and substituted amino acids at pH 5.2, 7.2, and 9.0. Neither enzyme showed evidence of esterase activity towards N-benzoyl-L-arginine methyl ester at pH 6.8. Hydrolysis of the A chain of oxidized insulin at pH 9 slows down markedly when the α-enzyme has cleaved the chain once; the initial fast cleavage can take place at linkages between residues 9 and 10, 10 and 11, and 12 and 13; more slowly cleaved linkages are between residues 3 and 4, and 8 and 9. Hydrolysis of the B chain by the α-enzyme at pH 9 is still faster and slows down when the chain has been cleaved twice. One fast cleavage is at the linkage between residues 18 and 19; the other can take place at the linkages between residues 12 and 13, and 14 and 15; more slowly cleaved linkages are between residues 8 and 9, 9 and 10, and 15 and 16. Under the conditions tested, the β-enzyme does not hydrolyze the A chain appreciably at pH 9. It cleaves the B chain rapidly at the linkage between residues 23 and 24 and more slowly at linkages between residues 18 and 19. The linkages split by both enzymes are those which involve the carboxyl group of a neutral amino acid.

THE OXIDATION OF ESTRONE-16-C14BY PEROXIDASE

1962 ◽  
Vol 40 (4) ◽  
pp. 459-469 ◽  
Author(s):  
P. H. Jellinck ◽  
Louise Irwin
Keyword(s):  
Amino Acids ◽  
Hydrogen Peroxide ◽  
Amino Acid ◽  
Serum Albumin ◽  
Oxidase Activity ◽  
Water Soluble ◽  
The Other ◽  
Aerobic Incubation ◽  
Nitrogenous Compounds ◽  
Initial Generation

Aerobic incubation of estrone-16-C14with peroxidase in the presence of serum albumin and other proteins resulted in the formation of water-soluble, ether-insoluble metabolites in high percentage yields. Similar products were formed when protein was replaced by cysteine or tryptophan but none of the other amino acids tested had any effect. The evidence points to an initial generation of hydrogen peroxide from these nitrogenous compounds by the enzyme acting as an aerobic oxidase, and the subsequent peroxidation of estrone to highly reactive products. These then combine with the protein or amino acid or else undergo alternative reactions. A strong chemical bond is formed with albumin and attempts to release the estrone metabolites from it were unsuccessful. Uterine homogenates from estrogen-treated rats showing high DPNH oxidase activity contained no "peroxidase" as measured by the formation of water-soluble products from estrone in the presence of protein.

Trunculin-F and Contrunculin-A and -B: Novel Oxygenated Norterpenes From a Southern Australian Marine Sponge, Latrunculia conulosa

1993 ◽  
Vol 46 (9) ◽  
pp. 1363 ◽  
Author(s):  
MS Butler ◽  
RJ Capon
Keyword(s):  
Methyl Ester ◽  
Natural Product ◽  
Marine Sponge ◽  
Coastal Waters ◽  
Spectroscopic Analysis ◽  
Marine Natural Product ◽  
New Compounds ◽  
Absolute Stereochemistry

A specimen of Latrunculia conulosa from southern Australian coastal waters, previously observed to contain conulosin-A (6) and conulosin-B (7), has also been found to yield the known marine natural product trunculin-C methyl ester (14), along with three new norterpenes, trunculin-F (10), contrunculin-A (11) and contrunculin-B (12). Trunculin-F (10) was isolated, characterized and identified as its methyl ester (13), and its absolute stereochemistry determined by Horeau analysis. The structures for all new compounds were secured by detailed spectroscopic analysis.

Activity of Plasmin and Streptokinase-Activator on Substituted Arginine and Lysine Esters

1966 ◽  
Vol 16 (01/02) ◽  
pp. 018-031 ◽  
Author(s):  
S Sherry ◽  
Norma Alkjaersig ◽  
A. P Fletcher
Keyword(s):  
Molecular Structure ◽  
Methyl Ester ◽  
Comparative Studies ◽  
Esterase Activity ◽  
Methyl Esters ◽  
Hydrolytic Activity ◽  
The Other ◽  
Other Hand

SummaryComparative studies have been made of the esterase activity of plasmin and the streptokinase-activator of plasminogen on a variety of substituted arginine and lysine esters. Human plasmin preparations derived by different methods of activation (spontaneous in glycerol, trypsin, streptokinase (SK) and urokinase) are similar in their esterase activity; this suggests that the molecular structure required for such esterase activity is similar for all of these human plasmins. Bovine plasmin, on the other hand, differs from human plasmin in its activity on several of the substrates studied (e.g., the methyl esters of benzoyl arginine and tosyl, acetyl and carbobenzoxy lysine), a finding which supports the view that molecular differences exist between the two animal plasmins. The streptokinase-activator hydrolyzes both arginine and lysine esters but the ratios of hydrolytic activity are distinct from those of plasmin and of other activators of plasminogen. The use of benzoyl arginine methyl ester as a substrate for the measurement of the esterase activity of the streptokinase-activator is described.

Gastrointestinal Interaction between Dietary Amino Acids and Gut Microbiota: With Special Emphasis on Host Nutrition

2020 ◽  
Vol 21 (8) ◽  
pp. 785-798 ◽  
Author(s):  
Abedin Abdallah ◽  
Evera Elemba ◽  
Qingzhen Zhong ◽  
Zewei Sun
Keyword(s):  
Amino Acids ◽  
Fatty Acids ◽  
Immune System ◽  
Gut Microbiota ◽  
Short Chain Fatty Acids ◽  
Nutrition And Health ◽  
Nitrogenous Compounds ◽  
Dietary Amino Acids ◽  
Host Nutrition ◽  
Chain Fatty Acids

The gastrointestinal tract (GIT) of humans and animals is host to a complex community of different microorganisms whose activities significantly influence host nutrition and health through enhanced metabolic capabilities, protection against pathogens, and regulation of the gastrointestinal development and immune system. New molecular technologies and concepts have revealed distinct interactions between the gut microbiota and dietary amino acids (AAs) especially in relation to AA metabolism and utilization in resident bacteria in the digestive tract, and these interactions may play significant roles in host nutrition and health as well as the efficiency of dietary AA supplementation. After the protein is digested and AAs and peptides are absorbed in the small intestine, significant levels of endogenous and exogenous nitrogenous compounds enter the large intestine through the ileocaecal junction. Once they move in the colonic lumen, these compounds are not markedly absorbed by the large intestinal mucosa, but undergo intense proteolysis by colonic microbiota leading to the release of peptides and AAs and result in the production of numerous bacterial metabolites such as ammonia, amines, short-chain fatty acids (SCFAs), branched-chain fatty acids (BCFAs), hydrogen sulfide, organic acids, and phenols. These metabolites influence various signaling pathways in epithelial cells, regulate the mucosal immune system in the host, and modulate gene expression of bacteria which results in the synthesis of enzymes associated with AA metabolism. This review aims to summarize the current literature relating to how the interactions between dietary amino acids and gut microbiota may promote host nutrition and health.

Selective cyclization modes of methyl 3′-heteroarylamino-2′-(2,5-dichlorothiophene-3-carbonyl)acrylates. Synthesis of model (thienyl)pyrazolo- and triazolo[1,5-α]pyrimidines

2020 ◽  
Vol 75 (12) ◽  
pp. 1037-1042
Author(s):  
Nuha I. Sweidan ◽  
Mustafa M. El-Abadelah ◽  
Musa Z. Nazer ◽  
Wolfgang Voelter
Keyword(s):  
Spectral Data ◽  
The Other ◽  
Keto Group ◽  
Other Hand ◽  
Selective Displacement ◽  
New Compounds

AbstractInteraction of methyl 3-ethoxy-2-(2,5-dichloro-3-thenoyl)acrylate (I) with 3-aminopyrazole and 3-amino-1,2,4-triazole generated the respective pyrazolo[1,5-α]pyrimidine (4) and triazolo[1,5-α]pyrimidine (7). The formation of 4 entails selective and consecutive displacement of the 3-ethoxy and methoxy (ester) anions in I by 3-NH2 and 1-NH of 3-aminopyrazole. On the other hand, the formation of 7 implies selective displacement of 3-ethoxy in I by the ring-NH followed by cyclocondensation involving the keto group in I and 3-NH2 of aminotriazole. This latter selective displacement sequence is also followed by 3-amino-5-hydroxypyrazole in its reaction with I. The structures of the new compounds are supported by microanalytical and spectral data.

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

Sign in / Sign up

Export Citation Format

Share Document