Evaluation of 2-(piperidine-1-yl)-ethyl (PIP) as a protecting group for phenols: Stability to ortho-lithiation conditions and boiling concentrated hydrobromic acid, orthogonality with most common protecting group classes, and deprotection via Cope elimination or by mild Lewis acids

Tetrahedron ◽  
2021 ◽  
pp. 132108
Author(s):  
Rolf Norén
Keyword(s):  
Lewis Acids ◽  
Hydrobromic Acid ◽  
Protecting Group

scholarly journals SnCl4-catalyzed Solvent-free Acetolysis of 2,7-Anhydrosialic Acid Derivatives

2019 ◽  
Author(s):  
Kesatebrhan Haile Asressu ◽  
Cheng-Chung Wang
Keyword(s):  
Sialic Acid ◽  
Lewis Acids ◽  
Ring Opening ◽  
Building Blocks ◽  
Solvent Free ◽  
Biologically Active ◽  
Protecting Group ◽  
Free Ring ◽  
Ring Opening Reactions ◽  
Acid Catalyzed

Sialic acid-containing glycans are found in different sialic acid forms and a variety of glycosidic linkages in biologically active glycoconjugates. Hence, the preparation of suitably protected sialyl building blocks requires high attention in order to access glycans in pure form. In this line, various C-5 substituted 2,7-anhydrosialic acid derivatives bearing both electron donating and withdrawing protecting groups were synthesized and subjected to different Lewis acid-catalyzed solvent free ring opening reactions at room temperature in the presence of acetic anhydride. Among the various Lewis acids tested, the desired acetolysized products were obtained in moderate yields under a tin(IV) chloride catalysis system. Our methodology can be extended to regioselective protecting group installation and manipulation towards a number of thiosialoside and halide donors.

scholarly journals Diastereoselective Pictet–Spengler Reactions of a Tethered 2-Aminoimidazole

2014 ◽  
Vol 67 (2) ◽  
pp. 184 ◽  
Author(s):  
Sudhir R. Shengule ◽  
Peter Karuso
Keyword(s):  
Amino Acid ◽  
Molecular Modelling ◽  
Lewis Acids ◽  
Side Chain ◽  
Amino Acid Side Chain ◽  
Protecting Group ◽  
Nmr Data ◽  
The Absolute ◽  
Absolute Stereochemistry

The diastereoselective Pictet–Spengler reaction of aminopropyl-2-aminoimidazole with enantiopure aldehydes has been investigated. With amino acid-derived aldehydes, anti stereochemistry is favoured, with a diastereoselectivity up to 92 % achievable. The absolute stereochemistry of the products was determined through synthesis of a rigid derivative and from NMR data in combination with molecular modelling. The diastereoselectivity was shown to be dependent on the steric bulk of the amino acid side chain and independent of the nitrogen protecting group. Lewis acids catalysed the reaction but did not affect the diastereoselectivity.

scholarly journals SnCl4-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

2019 ◽  
Vol 15 ◽  
pp. 2990-2999
Author(s):  
Kesatebrhan Haile Asressu ◽  
Cheng-Chung Wang
Keyword(s):  
Sialic Acid ◽  
Lewis Acids ◽  
Ring Opening ◽  
Building Blocks ◽  
Solvent Free ◽  
Biologically Active ◽  
Protecting Group ◽  
Free Ring ◽  
Ring Opening Reactions ◽  
Acid Catalyzed

Sialic acid-containing glycans are found in different sialic acid forms and a variety of glycosidic linkages in biologically active glycoconjugates. Hence, the preparation of suitably protected sialyl building blocks requires high attention in order to access glycans in a pure form. In line with this, various C-5-substituted 2,7-anhydrosialic acid derivatives bearing both electron-donating and -withdrawing protecting groups were synthesized and subjected to different Lewis acid-catalyzed solvent-free ring-opening reactions at room temperature in the presence of acetic anhydride. Among the various Lewis acids tested, the desired acetolysis products were obtained in moderate yields under tin(IV) chloride catalysis. Our methodology could be extended to regioselective protecting group installations and manipulations towards a number of thiosialoside and halide donors.

Synthesis and Structural Stability of α-Helical Gold(I)-Metallopeptidesy

Synlett ◽  
2020 ◽  
Author(s):  
Pol Besenius ◽  
Lydia Zengerling ◽  
Benedict Kemper ◽  
Ute A. Hellmich
Keyword(s):  
Lewis Acids ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Cd Spectroscopy ◽  
Side Chain ◽  
Protecting Group ◽  
Temperature Dependent ◽  
Phosphine Complexes ◽  
Boron Tribromide ◽  
Spectroscopy Studies

AbstractThe synthesis of hexa- and dodecapeptides functionalized with two Au(I)–phosphine complexes is reported. The high stability of the Au(I)–phosphine bond allowed orthogonal peptide-protecting-group chemistry, even when using hard Lewis acids like boron tribromide. This enabled the preparation of an Fmoc-protected lysine derivative carrying the Au(I) complex in a side chain, which was used in standard Fmoc-based solid-phase peptide synthesis protocols. Alanine and leucine repeats in the metallododecapeptide formed α-helical secondary structures in 2,2,2-trifluoroethanol–H2O and 1,1,1,3,3,3-hexafluoroisopropanol–H2O mixtures with high thermal stability, as shown by temperature-dependent CD spectroscopy studies.

Solification with Hydrobromic Acid as a Factor Defining the Antiarrhythmic Effect of Lappaconitine Derivatives

2009 ◽  
Vol 6 (7) ◽  
pp. 475-477 ◽  
Author(s):  
T. Tolstikova ◽  
A. Bryzgalov ◽  
I. Sorokina ◽  
S. Osadchii ◽  
E. Shults ◽  
...  
Keyword(s):  
Hydrobromic Acid ◽  
Antiarrhythmic Effect

Short Protecting Group-free Syntheses of CDE Synthon of Racemic Camptothecin

2020 ◽  
Vol 17 (7) ◽  
pp. 588-591
Author(s):  
Pingxuan Shao ◽  
Wei Lu ◽  
Lei Wang
Keyword(s):  
Total Synthesis ◽  
Future Development ◽  
Protecting Group ◽  
Short Route ◽  
The Future ◽  
Tricyclic Ketone

A practical and concise total synthesis of tricyclic ketone 7 (CDE ring), a valuable intermediate for the synthesis of racemic camptothecin and analogs, was described (8 chemical steps and 29% overall yield). The synthesis starts with two inexpensive, readily available materials and is operationally simple to perform. It is worth mentioning that the reported protecting group-free synthesis, with advantages of a short route, would be helpful for the future development of industry-scale syntheses of camptothecin-family alkaloids.

Fluoroquinolone-3-carboxamide Amino Acid Conjugates: Synthesis, Antibacterial Properties And Molecular Modeling Studies

2020 ◽  
Vol 17 (1) ◽  
pp. 71-84
Author(s):  
Riham M. Bokhtia ◽  
Siva S. Panda ◽  
Adel S. Girgis ◽  
Hitesh H. Honkanadavar ◽  
Tarek S. Ibrahim ◽  
...  
Keyword(s):  
Experimental Data ◽  
Antibacterial Activity ◽  
Amino Acid ◽  
Bacterial Infections ◽  
Antibacterial Agents ◽  
Antibacterial Properties ◽  
Computational Studies ◽  
Protecting Group ◽  
Amino Acid Conjugates ◽  
Molecular Modeling Studies

Background: Bacterial infections are considered as one of the major global health threats, so it is very essential to design and develop new antibacterial agents to overcome the drawbacks of existing antibacterial agents. Method: The aim of this work is to synthesize a series of new fluoroquinolone-3-carboxamide amino acid conjugates by molecular hybridization. We utilized benzotriazole chemistry to synthesize the desired hybrid conjugates. Result: All the conjugates were synthesized in good yields, characterized, evaluated for their antibacterial activity. The compounds were screened for their antibacterial activity using methods adapted from the Clinical and Laboratory Standards Institute. Synthesized conjugates were tested for activity against medically relevant pathogens; Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27856) Staphylococcus aureus (ATCC 25923) and Enterococcus faecalis (ATCC 19433). Conclusion: The observed antibacterial experimental data indicates the selectivity of our synthesized conjugates against E.Coli. The protecting group on amino acids decreases the antibacterial activity. The synthesized conjugates are non-toxic to the normal cell lines. The experimental data were supported by computational studies.

Participation of 19-ester groups in the cleavage of 2α,3α- and 5α,6α-steroid epoxides. A case of competition between participation and external nucleophile attack

1979 ◽  
Vol 44 (5) ◽  
pp. 1496-1509 ◽  
Author(s):  
Pavel Kočovský ◽  
Václav Černý
Keyword(s):  
Perchloric Acid ◽  
Hydrobromic Acid ◽  
Ester Group ◽  
Carbonyl Oxygen ◽  
Cyclic Carbonate ◽  
Cyclic Ether ◽  
Normal Reaction ◽  
Neighboring Group ◽  
Ether Oxygen ◽  
The Difference

Acid cleavage of the acetoxy epoxide IIIa with aqueous perchloric acid or hydrobromic acid gave two types of products, i.e. the diol Va or the bromohydrin VIa, and the cyclic ether VIII. The latter compound arises by participation of ether oxygen of the ester group. On reaction with perchloric acid the epoxide IVa gave the diol XIIIa as a product of a normal reaction and the isomeric diol Xa as a product arising by intramolecular participation of the carbonyl oxygen of the 19-acetoxy group. Participation of the 19-ester group is confirmed by the formation of the cyclic carbonate XI when the 19-carbonate IVb is treated analogously. On reaction with hydrobromic acid, the epoxide IVa gave solely the bromohydrin XIVa as a product of the normal reaction course. Discussed is the similarity of these reactions with electrophilic additions to the related 19-acetoxy olefins I and II, the mechanism, the difference in behavior of both epoxides III and IV, the dependence of the product ratio on the nucleophility of the attacking species, and the competition between participation of an ambident neighboring group and an external nucleophile attack.

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