Acetylation with acetic anhydride and

Because coupling is not always quantitative, the non-reacted terminal deoxynucteoside must be excluded from the following synthesis cycles. Otherwise deletion sequences will render the isolation of the pure final product difficult. Therefore a capping step (step 3) follows, e.g., acetylation with acetic anhydride and N,N-dimethyl-4-pyridinamine (DMAP) in dioxane. Capping times should be as short as possible, especially with 2-cyanoethyl phosphite triesters, which are sensitive to bases such as DMAP. 

Aminoimidazolium salts (78) have been synthesized by the reaction of jV,AT-disubstituted amidines (79) with a haloacetonitrile. The formation of the salts (78) proceeds via the intermediates (80) (71BCJ826, 71JOC3368). These salts (78) can be acetylated with acetic anhydride, and the halide ion (X ) replaced by perchlorate or picrate anions (71BCJ826). 

Lee [42] determined pentachlorophenol and 19 other chlorinated phenols in sediments. Acidified sediment samples were Soxhlet extracted (acetone-hexane), back extracted into potassium bicarbonate, acetylated with acetic anhydride and re-extracted into petroleum ether for gas chromatographic analysis using an electron capture or a mass spectrometric detector. Procedures were validated with spiked sediment samples at 100,10 and lng chlorophenols per g. Recoveries of monochlorophenols and polychlorophenols (including dichlorophenols) were 65-85% and 80-95%, respectively. However, chloromethyl phenols were less than 50% recovered and results for phenol itself were very variable. The estimated lower detection limit was about 0.2ng per g. 

The unprotected amine was acetylated with acetic anhydride and the nitrile was converted to the ethyl ester in acidic ethanol with concomitant removal of the Boc group to provide oseltamivir. Finally, salt formation with 85% phosphoric acid in ethanol afforded oseltamivir phosphate (1). 

Mannitol hexanitrate is obtained by nitration of mannitol with mixed nitric and sulfuric acids. Similarly, nitration of sorbitol using mixed acid produces the hexanitrate when the reaction is conducted at 0—3°C and at —10 to —75°C, the main product is sorbitol pentanitrate (117). Xylitol, ribitol, and L-arabinitol are converted to the pentanitrates by fuming nitric acid and acetic anhydride (118). Phosphate esters of sugar alcohols are obtained by the action of phosphorus oxychloride (119) and by alcoholysis of organic phosphates (120). The 1,6-dibenzene sulfonate of D-mannitol is obtained by the action of benzene sulfonyl chloride in pyridine at 0°C (121). To obtain 1,6-dimethanesulfonyl-D-mannitol free from anhydrides and other by-products, after similar sulfonation with methane sulfonyl chloride and pyridine the remaining hydroxyl groups are acetylated with acetic anhydride and the insoluble acetyl derivative is separated, followed by deacetylation with hydrogen chloride in methanol (122). Alkyl sulfate esters of polyhydric alcohols result from the action of sulfur trioxide—trialkyl phosphates as in the reaction of sorbitol at 34—40°C with sulfur trioxide—triethyl phosphate to form sorbitol hexa(ethylsulfate) (123). 

On reduction with stannous chloride it yielded 3-aminoperchloryl benzene, in the form of colourless needles, m.p. 30-31°C. By acetylation with acetic anhydride and acetic acid it yielded 3-perchlorylacetanilide (m.p. 136-137°C). 

Benzofuran-3(2/f)-ones (396) exist in the keto form but undergo ready enolization. Acetylation with acetic anhydride and sodium acetate affords 3-acetoxybenzo[6]furans, but reaction under acidic conditions usually supplies these products admixed with 3-acetoxy-2-acetylbenzo[6]furans. Alkylation usually furnishes a mixture of O- and C-alkylated products. 3-Acetoxy-6-methoxy-4-methylbenzo[6]furan, on Vilsmeier reaction, supplies the 3-chlorobenzo[6]furan-2-carbaldehyde, the product expected from an enolizable ketone (72AJC545). Benzofuran-3(2//)-ones react normally with carbonyl reagents. Grignard reagents react in the expected way and dehydration of the intermediate affords a 3-substituted benzo[6]furan. The methylene group is reactive so that self condensation, condensation with aldehydes and ketones and reaction with Michael acceptors all occur readily. 

Hydroxy-2-oxo-3,4-dihydropyrido[l,2-a]pyrimidine was O-acetylated with acetic anhydride and dehydrated to 2-oxo-2//-pyrido[l,2-u]pyrimidine (18) with phosphorus pentoxide.200... 

To 119 g (0.45 mol) of N-(2-diethylaminoethyl)-2-methoxy-4-aminobenzamide dissolved in 200 cc of acetic acid are added in the cold in small portions 69 g of acetic anhydride (0.45 mol + 50% excess). The starting material is made by esterifying 4-aminosalicylic acid with methanol, then acetylating with acetic anhydride and then methylating with dimethyl sulfate. The solution obtained is heated for 2 hours on a water bath and then boiled for 15 minutes. It is cooled at 25°C. While agitating constantly and maintaining the temperature between 25° and 30°C, there is added to the solution drop by drop 72 g of bromine dissolved in 60 cc of acetic acid. It is agitated for one hour. The... 

Cyclization of enone (9) in hexane with boron trifluorideetherate in presence of 1,2-ethanedithiol, followed by hydrolysis with mercury (II) chloride in acetonitrile, yielded the cis-isomer (10) (16%) and transisomer (11) (28%). Reduction of (10) with lithium aluminium hydride in tetrahydrofuran followed by acetylation with acetic anhydride and pyridine gave two epimeric acetates (12) (32%) and (13) (52%) whose configuration was determined by NMR spectroscopy. Oxidation of (12) with Jones reagent afforded ketone (14) which was converted to the a, 3-unsaturated ketone (15) by bromination with pyridinium tribromide in dichloromethane followed by dehydrobromination with lithium carbonate and lithium bromide in dimethylformamide. Ketone (15), on catalytic hydrogenation with Pd-C in the presence of perchloric acid, produced compound (16) (72%) and (14) (17%). The compound (16) was converted to alcohol (17) by reduction with lithium aluminium hydride. 

Hydrolysis of deferriferricrocin in 57% HI gives serine, glycine, alanine, ornithine and ammonia in the molar ratios 0.25 2.00 0.68 3.05 0.04 no alanine is found on hydrolysis in 6N HCI. Treatment with IN HCI at 100° for 15 min. gives substance with negative ferric chloride test. Re-acetylation with acetic anhydride and removal of O-acetyl affords a product with chromatographic properties of ferricrocin. 

Extranuclear acetoxyalkylpyrazines have been prepared from hydroxyalkyl-pyrazines by acetylation with acetic anhydride and dry pyridine as follows 2-methyl-6-(D-flraho-tetraacetoxybutyl)pyrazine (182), 2,5-bis(D-araho-tetraacetoxybutyl)-pyrazine (182), and 2-acetoxymethyl-3-aminopyrazine (1075) and 2-methyI-5-(D-3-(D- 0 pyrazine with benzoyl chloride and dry pyridine (182). 

Compound 10a has been acetylated with acetic anhydride and an aqueous solution of sodium acetate in presence of hydrochloric acid to give the product 10b. 

N-Acetoxyphthalimide (2). The reagent is prepared by reaction of sodium N-hydroxy-phthalimide (which see) with acetyl chloride. It is recommended specifically - for N-acetylation of muramlc acid (1), since acetylation with acetic anhydride and pyridine gives products of intramolecular cyclization (lactams). Osawa and Jeanloz treated a solution of (1) in methanol at 0° with 2 equivalents of the reagent and 1 equivalent of triethylamine and let the mixture stand at room temperature for 20 hrs. 

Fritz and Schenk effected acetylation with acetic anhydride and perchloric acid in ethyl acetate at room temperature, and this combination proved effective for conversion of the 8-keto acid (1) into the lactone (2). In the original procedure of... 

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