A convenient protection for 4-oxopyrimidine moieties in nucleosides by the pivaloyl group

2010 ◽  
Vol 75 (1) ◽  
pp. 33-57 ◽  
Author(s):  
Michał Sobkowski
Keyword(s):  
Selective Removal ◽  
Protecting Group ◽  
Experimental Conditions ◽  
Reaction Proceeding ◽  
Mild Conditions ◽  
Acidic Conditions ◽  
Rapid Reaction

Application of the pivaloyl group as a protection for the N3 position of thymidine and uridine was investigated. Pivaloylation of thymidine is a very rapid reaction proceeding under mild conditions with excellent regioselectivity for sugar or thymine moiety, depending on the amines used. Several pivaloylated thymidine derivatives were obtained by treatment of unprotected thymidine with pivaloyl chloride under various experimental conditions. Stability of the N3-pivaloyl protecting group under basic and acidic conditions was evaluated and the conditions for its selective removal were found.

2-Naphthylmethyl (NAP) as a Versatile Amino Protecting Group, Chemo­selective Removal under Mild Conditions

Synlett ◽  
2003 ◽  
pp. 2065-2067
Author(s):  
Philippe Compain ◽  
Olivier R. Martin ◽  
Guillaume Godin
Keyword(s):  
Protecting Group ◽  
Mild Conditions

scholarly journals A Three-Step Process for the Bioconversion of Whey Permeate into a Glucose-Free D-Tagatose Syrup

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 647 ◽  
Author(s):  
Fadia V. Cervantes ◽  
Sawssan Neifar ◽  
Zoran Merdzo ◽  
Javier Viña-Gonzalez ◽  
Lucia Fernandez-Arrojo ◽  
...  
Keyword(s):  
Bacillus Stearothermophilus ◽  
Cheese Whey ◽  
Bifidobacterium Bifidum ◽  
Rare Sugar ◽  
Experimental Conditions ◽  
Whey Permeate ◽  
Mild Conditions ◽  
Stage Process ◽  
Short Time ◽  
Arabinose Isomerase

We have developed a sustainable three-stage process for the revaluation of cheese whey permeate into D-tagatose, a rare sugar with functional properties used as sweetener. The experimental conditions (pH, temperature, cofactors, etc.) for each step were independently optimized. In the first step, concentrated whey containing 180–200 g/L of lactose was fully hydrolyzed by β-galactosidase from Bifidobacterium bifidum (Saphera®) in 3 h at 45 °C. Secondly, glucose was selectively removed by treatment with Pichia pastoris cells for 3 h at 30 °C. The best results were obtained with 350 mg of cells (previously grown for 16 h) per mL of solution. Finally, L-arabinose isomerase US100 from Bacillus stearothermophilus was employed to isomerize D-galactose into D-tagatose at pH 7.5 and 65 °C, in presence of 0.5 mM MnSO4. After 7 h, the concentration of D-tagatose was approximately 30 g/L (33.3% yield, referred to the initial D-galactose present in whey). The proposed integrated process takes place under mild conditions (neutral pH, moderate temperatures) in a short time (13 h), yielding a glucose-free syrup containing D-tagatose and galactose in a ratio 1:2 (w/w).

AB loop engineered ferritin nanocages for drug loading under benign experimental conditions

2019 ◽  
Vol 55 (82) ◽  
pp. 12344-12347 ◽  
Author(s):  
Wenming Wang ◽  
Lele Wang ◽  
Guobang Li ◽  
Guanghua Zhao ◽  
Xuan Zhao ◽  
...  
Keyword(s):  
Drug Loading ◽  
Selective Removal ◽  
Experimental Conditions

Selective removal of several residues from the AB loop of ferritin makes it more suitable for drug loading under benign experimental conditions.

Introduction of 4-Chlorophenyl: A Protecting Group for the Hydroxy Function

Synlett ◽  
2018 ◽  
Vol 29 (11) ◽  
pp. 1510-1516 ◽  
Author(s):  
Koichi Fukase ◽  
Yuji Otsuka ◽  
Toshihiro Yamamoto
Keyword(s):  
Hydroxy Group ◽  
Copper Catalyst ◽  
Pd Catalyst ◽  
Protecting Group ◽  
Acidic Conditions ◽  
Initial Conversion

4-Chlorophenyl ether was utilized as a new protecting group for the hydroxy function. This group was readily introduced to a sugar hydroxy group by using diaryliodonium triflate. Regioselective introduction of this protecting group at the vicinal cis-diol was achieved by using a copper catalyst and diaryliodonium triflate. This protecting group is stable under the Lewis acidic conditions of glycosylation, but it can be readily removed by the initial conversion into the corresponding 4-methoxyphenyl ether with use of a Pd catalyst, followed by oxidation with ammonium cerium (IV) nitrate [(NH4)2Ce(NO3)6] (CAN).

Photocatalytic Cr(VI) Reduction by Anodized TiO2

2008 ◽  
Vol 569 ◽  
pp. 221-224 ◽  
Author(s):  
Jae Kyung Yoon ◽  
Eun Jung Shim ◽  
Jin Wook Ha ◽  
Hyun Ku Joo
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Production ◽  
Zeta Potential ◽  
Environmental Remediation ◽  
Annealing Temperature ◽  
Experimental Conditions ◽  
Novel Technique ◽  
Reduction Efficiency ◽  
Lower Annealing Temperature ◽  
Acidic Conditions

In this study, immobilized nanotubular TiO2 is used to reduce toxic Cr(VI) to non toxic Cr(III) in aqueous solution under UV irradiation. To overcome the limitation of powder TiO2, a novel technique of immobilization based on anodization was applied and investigated under various experimental conditions. Among the samples tested under same anodizing condition, the nanotubular TiO2 annealed at 450 oC and 550 oC showed higher reduction efficiencies of Cr(VI). In addition, the surface characterizations (zeta potential, XRD and SEM) of these samples proved that the Cr(VI) reduction efficiency was higher under acidic conditions and at a lower annealing temperature. Through this study, it was concluded that anodized TiO2 has the potential to be useful technology for environmental remediation as well as hydrogen production in water.

The 2,2,2-Trichloroethyl Group for Carboxyl Protection During Peptide Synthesis

1973 ◽  
Vol 51 (2) ◽  
pp. 208-214 ◽  
Author(s):  
Bernard Marinier ◽  
Yoon C. Kim ◽  
Jean-Marie Navarre
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Peptide Synthesis ◽  
Optical Activity ◽  
Selective Removal ◽  
Acid Chlorides ◽  
Protecting Group

The 2,2,2-trichloroethyl esters of several N-carbobenzoxy-amino acids were prepared by reacting the corresponding acid chlorides with trichloroethanol and the carbobenzoxy groups were selectively removed by HBr–AcOH. The resulting esters were then coupled with various N-carbobenzoxy-amino acids or peptides using dicyclohexylcarbodiimide in acetonitrile to give N-carbobenzoxy-peptide trichloroethyl esters. The selective removal of the trichloroethyl protecting group was effected by reduction using zinc in acetic acid. The optical activity of the N-carbobenzoxy-peptides so obtained agreed well with the values reported in the literature. The overall results suggest that the 2,2,2-trichloroethyl group could be useful for carboxyl protection during peptide synthesis.

Total synthesis of (±)-9-deoxygoniopypyrone. Application of the iodocyclofunctionalization reaction of bold α-allenic alcohol derivatives

1998 ◽  
Vol 76 (1) ◽  
pp. 94-101 ◽  
Author(s):  
Richard W Friesen ◽  
Suzanne Bissada
Keyword(s):  
Total Synthesis ◽  
Primary Alcohol ◽  
Silyl Ether ◽  
Protecting Group ◽  
Acetylenic Ester ◽  
The Third ◽  
Vicinal Diol ◽  
Epoxide Opening ◽  
Vinyl Iodide ◽  
Acidic Conditions

The synthesis of ( ±)-9-deoxygoniopypyrone (1) from the α-allenic alcohol 5 is described. Iodocyclofunctionaliztion of the N-tosyl carbamate derivative of 5 using I2 and Ag2CO3 provided, in a highly diastereoselective and regioselective fashion, the vinyl iodo syn-vicinal diol 4. Two routes were explored in order to introduce the third stereogenic centre in the molecule. Reductive deiodination of the vinyl iodide and diastereoselective epoxidation of the derived acetonide14 using mCPBA provided a mixture of epoxides 15 and 16 (2:1) in which the desired threo diastereomer predominated. Alternatively, dihydroxylation of acetonide 14 (OsO4, NMO) yielded a mixture of diols 21 and 22 (2:3) which were separated after monosilylation (TBDMSCl) of the primary alcohol. The major silyl ether erythro diastereomer 24 was converted to the desired epoxide 15 by mesylation (MsCl, Et3N) and epoxide formation (TBAF) with inversion of stereochemistry. The minor threo diastereomer 23 was also converted to the desired epoxide 15 (TBAF; ArSO2Cl; NaOMe). Epoxide opening was effected with lithium acetylide and the resulting alkyne 27 was carbonylated (MeLi, ClCO2Me) to afford the α , β-acetylenic ester 28. Semi hydrogenation over Lindlar's catalyst followed by protecting- group removal under acidic conditions provided ( ±)-8-epigoniodiol 30. Finally, conversion of 30 to ( ±)-9-deoxygoniopypyrone 1 was effected under basic conditions (DBU).Key words: ( ±)-9-deoxygoniopypyrone, α-allenic alcohol, iodocyclofunctionalization, syn-diol.

scholarly journals Selective Removal ofN-Boc Protecting Group from Aromatic Amines Using Silica Gel-Supported Sodium Hydrogen Sulfate and HY-Zeolite as Heterogeneous Catalysts[1]

2003 ◽  
Vol 345 (11) ◽  
pp. 1207-1208 ◽  
Author(s):  
N. Ravindranath ◽  
C. Ramesh ◽  
M. Ravinder Reddy ◽  
Biswanath Das
Keyword(s):  
Silica Gel ◽  
Aromatic Amines ◽  
Heterogeneous Catalysts ◽  
Selective Removal ◽  
Hydrogen Sulfate ◽  
Protecting Group ◽  
Hy Zeolite ◽  
Sodium Hydrogen

The 2,2,2-Trichloro-tert-butyloxycarbonyl Group(TCBOC)—An Acid- and Base-Resistant Protecting Group Removable under Mild Conditions

1978 ◽  
Vol 17 (5) ◽  
pp. 361-362 ◽  
Author(s):  
Heiner Eckert ◽  
Monika Listl ◽  
Ivar Ugi
Keyword(s):  
Protecting Group ◽  
Mild Conditions ◽  
Acid And Base
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