Search results for "acetic anhydride"
showing 10 items of 21 documents
Role of SH-Groups and S-S Bridges in the Main Subunit (1/12 Molecule) of Spirographis Spallanzanii Chlorocruorin
1986
In all species of annelids described, the extracellular hemoglobins show (by electron microscopy) the same quaternary structure constituted by twelve identical subunits. The fine structure of the 1/12 subunit is not well resolved and several models have been proposed for it (2).
Zur Acetylierung von Spironolacton, Canrenon und 2-Methylencanrenon
1995
Bei der Umsetzung der Titelverbindungen mit Acetanhydrid und Acetylchlorid werden das 3,5-Dien-3-yl-acetat 2, die isomeren 2,4,6- und 3,5,7-Trien-3-yl-acetate 3 und 4 sowie das 2,4,6,8(14)-Tetraen-3-yl-acetat 7 erhalten. Hydrolyse von 7 liefert das 2α-Methl-8,14-didehydro-canrenon (9). 7 und 9 wurden auf ihre Bindungsfahigkeit gegenuber Hormon-Rezeptoren sowie den Serumproteinen SHBG und CBG gepruft: Die Substanzen erwiesen sich als inaktiv. Acetylation of Spironolactone, Canrenone, and 2-Methylene Canrenone Reaction of the title compounds with acetic anhydride and acetyl chloride yields the 3,5-dien-3-yl acetate 2 the isomeric 2,4,6- and 3,5,7-trien-3-yl acetates 3 and 4 as well as the 2,4…
An efficient acetylation of dextran using in situ activated acetic anhydride with iodine
2010
A facile, efficient, cost-effective and solvent-free acetylation method has been developed for the acetylation of dextran. Dextran acetates were successfully synthesized using different molar ratios of acetic anhydride in the presence of iodine as a catalyst without the use of any solvent. The reactions were realized at 50?C for 3 h under stirring and nitrogen. This efficient method yielded highly pure and organosoluble dextran esters. The reaction appears highly effective for obtaining higher degrees of substitution (DS) with great efficiency. Under solvent-free conditions, dextran triacetates were efficiently synthesized. It was also observed that the molar ratio can easily control the DS…
Gas chromatography-mass spectrometry characterization of the varnish and glue of an ancient 18th century double bass.
2007
A GC–MS investigation is conducted on the double bass “Panormus”, property of Conservatorio di Musica “Vincenzo Bellini” in Palermo. The most important components of the varnish (fatty acids) and of the glue (proteinaceous amino acids), with which the musical instrument was treated in the past, are determined. The analyses are carried out by prior derivatization of fatty acids by acidic methanol and of amino acids by acidic methanol and trifluoroacetic anhydride (TFAA). Analytes identification is achieved by direct comparison with several reference materials and the use of a digitized library.
The mechanism of formation of 3H,9H-Pyrano[3,4-b]indol-3-ones from 3-indolalkanoic acids
1991
The mechanism of the formation of 1-methyl-3H,9H-pyrano[3,4-b]indol-3-one (4) from the corresponding 3-indolacetic acid 1 is discussed. The suggested mechanism is substantiated by the isolation of a stable intermediate 2 and its transformations in the presence of acetic anhydride and/or Lewis acids.
Susceptibility of Methyl 3-Amino-1H-pyrazole-5-carboxylate to Acylation
2009
Abstract In the search for a new method of synthesis of hybrid peptides with aminopyrazole carboxylic acid, we tried to force selective acylation at the aromatic amino group instead of at the ring nitrogen atom with fairly gentle acylating agents. The acylating agents used were acid anhydrides: acetic anhydride, tert-butyl pyrocarbonate, and 2-(2-methoxyethoxy)ethoxyacetic acid/dicyclohexylcarbodiimide. We succceded in acylation at this amino group with almost none at the ring nitrogen atom. Sometimes, however, acylation in small quantities at the ring nitrogen atom was observed as a by-product. To remove this by-product, imidazole was used. Thus, we were able to obtain the hybrid peptides …
Eine oligomeranaloge friessche umlagerung oligomerer 2-acetoxy-1,3-phenylenmethylene
1979
α-Hydro-ω-hydroxypoly(5-chloro-2-hydroxy-1,3-phenylenemethylene)s (1a, b), the oligomeric condensation products from 4-chloro-2,6-bis(hydroxymethyl)phenol and 4-chlorophenol with hydrochloric acid in 1,4-dioxane, could be completely dehalogenated at room temperature and atmospheric pressure with hydrogene/Raney-Ni. The resulting oligomers 2a, b were esterified with acetic anhydride, and the esters 3a, b were subjected to a oligomer analogous Fries rearrangement to form the linear α-hydro-ω-hydroxypoly(5-acetyl-2-hydroxy-1,3-phenylenemethylene)s 4a and 4b. The characterization of the products was mainly done by spectroscopic methods.
New synthesis of condensed heterocycles from isoxazole derivatives VI. 2,5-Dimethyl-3-aeetyl-7-amino-1H-pyrrolo[3,2-b] pyridine
1978
A new synthesis of pyrrolo[3,2-b] pyridine starting with pyrrole ring is described. The procedure allows the synthesis of 4-azaindoles bearing a sensitive group at C-7. The nitration of 4b with nitric acid and acetic anhydride at −15° gave 5. The hydrogenation of 5 led to simultaneous reduction of N-hydroxy and nitro groups and to hydrogenolysis of the isoxazole nucleus, affording an appropriate chain of atoms to building up the pyrrolo[3,2-b] pyridine ring.
N-trifluoracetyl-nylon 66 als polymeres reagenz
1979
N-Trifluoroacetyl-Nylon 66 (2) obtained by the reaction of Nylon 66 (1) with trifluoroacetic anhydride is very suitable as a polymeric reagent for the trifluoroacetylation of amines and alcohols. The advantages of 2 compared with low molecular trifluoroacetylating reagents are discussed. The selectivity against different substituted anilines and against structurally isomeric secondary amines was studied intensively by kinetic measurements.
Palladium-Catalyzed Hydroxycarbonylation of Aryl and Vinyl Bromides by Mixed Acetic Formic Anhydride
2006
The palladium-catalyzed hydroxycarbonylation of aryl and vinyl bromides in the presence of acetic anhydride and lithium formate as a carbon monoxide source has been developed. The combination of palladium(II) acetate with 1,1'-bis(diphenylphosphino)ferrocene (dppf) is an efficient catalytic system when the reaction is carried out at 120 °C.