N-Acetylation with

Isatin (190) is a compound with interesting chemistry. It can be N- acetylated with acetic anhydride, N- methylated via its sodium or potassium salt and O- methylated via its silver salt. Oxidation of isatins with hydrogen peroxide in methanolic sodium methoxide yields methyl anthranilates (8lAG(E)882). In moist air, O-methylisatin (191) forms methylisatoid (192). Isatin forms normal carbonyl derivatives (193) with ketonic reagents such as hydroxylamine and phenylhydrazine and the reactive 3-carbonyl group also undergoes aldol condensation with active methylene compounds. Isatin forms a complex derivative, isamic acid (194), with ammonia (76JCS(pi)2004>. 

The resistance of Bacillus cereus cell-wall peptidoglycan to lysozyme action200 is due to the majority of the 2-amino-2-deoxy-D-glucosyl residues having free (nonsubstituted) amino groups. Polysaccharide and peptide components of the cell walls were converted into material susceptible to lysozyme by N-acetylation with acetic anhydride. 

Proof that 5-amino-5-deoxy-D-xylose exists in the six-membered ring-form 34 was afforded by the following reactions. N-Acetylation with acetic anhydride in alkaline solution gives 5-acetamido-5-deoxy-D-xylopyranose (35) (see Section III, 1, p. 167), isolated - in a yield of 45-50% no furanose form is found in the mother liquor. Reduction with sodium borohydride gives only the piperidine derivative 32 and no 5-amino-5-deoxy-D-xylitol. Catalytic hydrogenation affords 32 in quantitative yield. However, the latter reaction does not suffice to prove the exclusive presence of the six-membered ring-form 34, (29) S. Hanessian, Chem. Ind. (London), 2126 (1966). 

The sulfonamides are nearly completely absorbed from the gastrointestinal tract. Once absorbed they are bound to protein (60% to 90%), mainly to albumin, and are distributed to all tissue. Metabolism is by N-acetylation, with the products having no antimicrobial activity. 

A further aldol condensation employing 56 has been reported [13, 28], The chiral linker 56 was N-acetylated with hydrocinnamoyl chloride and finally treated with isovaleraldehyde. The afforded [3-hydroxylated immobilized product was detached... 

F. e., also catalysis of the N-acetylation with BF3-etherate and G-acetylation in the presence of AIGI3, s. Y. Ueno, T. Takaya, and E. Imoto, Bull. Ghem. Soc. Japan 57, 864 (1964). 

Samples (2 mg) of the proteins were methanolyzed with methanol-1.5 M HCl and N-acetylated with acetic anhydride (19). The determination of methyl glycosides as their trimethylsilyl ethers was carried out by gas-liquid chromatography (20). 

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. 

Acetamidothiazole and its 4-alkyl derivatives react with chloro-sulfonic acid. The structure of the resulting products was a subject of controversy (172. 393-397). N-acetyl-A -(2-thiazolyl)-sulfamoyl chlorides (189) first proposed were then shown to be 2-acetamido-5-chloro-sulfonylthiazoles (190) (Scheme 120) (367. 368. 398). the latter assignment is based on infrared (368) and chemical evidence (367). 

Various 4-, 5-, or 4,5-disubstituted 2-aryIamino thiazoles (124), R, = QH4R with R = 0-, m-, or p-Me, HO C, Cl, Br, H N, NHAc, NR2, OH, OR, or OjN, were obtained by condensing the corresponding N-arylthiourea with chloroacetone (81, 86, 423), dichloroacetone (510, 618), phenacyichloride or its p-substituted methyl, f-butyl, n-dodecyl or undecyl (653), or 2-chlorocyclohexanone (653) (Method A) or with 2-butanone (423), acetophenone or its p-substituted derivatives (399, 439), ethyl acetate (400), ethyl acetyl propionate (621), a- or 3-unsaturated ketones (691), benzylidene acetone, furfurylidene acetone, and mesityl oxide in the presence of Btj or Ij as condensing agent (Method B) (Table 11-17). 

Amide resonance within the N acetyl group competes with delocalization of the nitro gen lone pair into the ring... 

More recendy the cis and trans isomers of the mosquito repellent CIC-4, a mixture of citroneUa isomers, have been separated by preparative hplc and bioassayed for effectiveness (23). Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazoUdine derivatives of (+)-and ( —)-citroneUal have been studied to find stmcture—activity relationships (24). Several 2-aLkyl- -acetyloxahdines have been synthesized and tested against mosquitoes, with further efforts using nmr to determine the rotational isomers of the more active N-acetyl-2,2-dimethyloxazohdine (25). 

AcOCgFs, Et3N, DMF, 80°, 12-60 h, 72-95% yield. This reagent reacts with amines (25°, no Et3N) selectively in the presence of alcohols to form N-acetyl derivatives in 80-90% yield. 

Purification as their N-acetyl derivatives is satisfactory for primary, and to a limited extent secondary, amines. The base is refluxed with slightly more than one equivalent of acetic anhydride for half to one hour, cooled and poured into ice-cold water. The insoluble derivative is filtered off, dried, and recrystallised from water, ethanol, aqueous ethanol or benzene (CAUTION toxic ). The derivative can be hydrolysed to the parent amine by refluxing with 70% sulfuric acid for a half to one hour. The solution is cooled, poured onto ice, and made alkaline. The amine is steam distilled or extracted as above. Alkaline hydrolysis is very slow. 

The preparation of enamines by reduction of aromatic heterocyclic bases and their quaternary salts or of lactams is not the most useful approach (97). The lithium aluminum hydride reduction of N-acyl enamines has been used with both fruitful and unsuccessful results. A series of 3-N-acetyl -d -cholestenes (104) has been prepared by desulfurization of the appropriate thiazolidine (105) (98,99). Lithium aluminum hydride reduction of the... 

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