A -acetyl derivative

Sulphonamides upon heating with acetyl chloride are converted into the A -acetyl derivatives or sulphonacetamides ... 

Controlled halogenation can be achieved by halogenation of the A/-acetyl derivative of the aromatic amine, followed by hydrolysis of the acetyl... 

In a few cases, A/ -heterocycHc sulfanilamides have been prepared by the condensation of an active heterocycHc haHde with the sulfonamide nitrogen of sulfanilamide or its A/-acetyl derivative in the presence of an acid-binding agent. Sulfapyridine, sulfadiazine, and sulfapyrazine have been made by this method (1), but the most important appHcation is probably for the synthesis of sulfachlorapyridazine (9) and sulfamethoxypyridazine (10) (45). 

A -Heterocyclic-A -acetylsulfanilamides. These derivatives may be prepared by condensation of the heterocycUc amine with /)-nitroben2enesu1fony1 chloride foUowed by acetylation of the nitro compound. The product may be reduced under mild conditions to give the 4-amiQO-A/ -heterocychc-A/ -acetyl derivative. Other approaches, however, have been developed (46,47). 

The most characteristic coupling constant in indazoles is the cross-ring Vs, present both in indazoles and in isoindazoles unsubstituted in positions 3 and 7. 2-Methyl isomers show an additional Vmc.h coupling which can serve to identify an isoindazole unsubstituted in position 3. In 3-azidoindazole, as in 3-azidopyrazole (56), the prototropic exchange is slowed down sufficiently to allow the measurement of a zig-zag /i,4 coupling constant. The deshielding effects observed in A-acetyl derivatives, e.g. 1-acetyl (60) on H-7 and 2-acetyl (61) on H-3, are related to a preferred E conformation (Section 4.04.1.4.3). 

Pellotine and Anhalonidine. The A -acetyl derivative of mezcaline (I NHj— NHAc), on treatment with phosphoric oxide, yields 6 7 8-trimethoxy-l-methyl-3 4-dihydrowoquinoline (picrate, m.p. 181-2°), which, on successive catalytic hydrogenation and treatment with methyl sulphate, yields 6 7 8-trimethoxy-l 2-dimethyl-l 2 3 4-tetrahydro-isoquinoline identical with 0-methylpellotine (picrate, m.p. 167-8°), whence it appears that pellotine must be a dimethyl ether of 6 7 8-trihydroxy-1 2-dimethyl-l 2 3 4-tetrahydrowoquinoline. Pellotine and anhalonidine on complete methylation yield the same product, and as anahalonidine is a secondary base and differs from pellotine by containing —CHj less, it must be a dimethyl ether of 6 7 8-trihydroxy-l-methyl-1 2 3 4-tetrahydrowoquinoline, and pellotine should be A -methyl-anahalonidine. 

A later variation of the general method, which extends the scope to 20-ketones, involves reaction of the ketone with benzylamine to give the imine, followed by conversion to the A-acetyl derivative with acetic anhydride. Although the resulting compound also has a A -double bond, it does not react sufficiently fast with peracid, and a A -double bond can not be preserved. 

ACOC6F5, 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 A-acetyl derivatives in 80-90% yield. 

As expected, compounds of type 78 possess an acidic hydrogen and readily form A-acetyl derivatives. The acetyl group is removed by warming with aqueous ammonia, and it is replaced by a methyl group when the compound is treated with alkaline dimethyl sulfate or excess diazomethane. 

A -Acetyl derivatives 125 and 126 exist as tautomerie mixtures in DMSO-dg at room temperature (for both, A [a]/[t] = 1-5) at elevated temperature the proportion of the azido form inereased. In CDCI3, the azido form only was deteeted for 125 for 126, a 126A 126T ratio was ehanged to 10 1. 

The tetrahydro-l,3-oxazines which contain a free A -hydrogen atom can be iV-acylated and A -nitrosated. - Certain A-substituted derivatives of tetrahydro-l,3-oxazin s can also react with acetic anhydride to form A -acetyl derivatives. > Most tetrahydro-l,3-oxazines add methyl iodide to form quaternary... 

Crystal-structure-sensitive bond-forming and -breaking processes other than ring-chain tautomerism are also known. For example, acetylation of 4-pyridone in pyridine gives rise to crystalline A-acetyl-4-pyridone. When this is dissolved in CH2C12 it gives a nearly 1 1 equilibrium mixture of this acetyl pyridone and 4-acetoxypyridine. The A-acetyl derivative is obtained by crystallization (79). 

D-Giucosamine and o-gaiactosamine, usually as A-acetyl derivatives, are part of the structures of several natural polysaccharides, whilst other uncommon aminosugars are components of the aminoglycoside antibiotics. We have also noted the occurrence of A-glycosides, where the nitrogen substitution is at the anomeric centre (see Box 12.3). 

This enzyme [EC 4.1.3.20] catalyzes the reaction of N-acylneuraminate 9-phosphate with phosphate to produce A-acetylmannosamine 6-phosphate, phosphoenolpyr-uvate, and water. The protein will act on A-glycoloyl and A-acetyl derivatives. 

The A-acetyl derivatives of the 2-alkylthio-l,3-thiadiazol-4-imines (124, R = SR, R = Ac) undergo nucleophilic displacement reaction with amines (benzylamine, cyclohexylamine, morpholine, or aniline) giving the 2-amino derivatives (124, R = NRj, R = Ac). The salt (126, R = R = Ph, R = R = H, X = Cl) reacts with aniline at room temperature giving 4-anilino-2-phenyl-l,3-thiazole (128), presumably by a mechanism involving cleavage of the heterocyclic ring. ... 

Methylene-substituted tetrahydro-l,3-oxazine 141 underwent ring opening in response to nucleophilic attack by carboxylic acids or thiophenols to afford the A -acetyl derivatives of the corresponding 0-acyl-l,3-amino alcohols 168 or aminoalkyl sulfides 169 in high yields (Scheme 27) <2006JC0262>. 

Benz, F.W., Nerland, D.E., Pierce, W.M. Babiuk, C. (1990) Acute aciylonitrile toxicity studies on the mechanism of the antidotal effect of D- and L-cysteine and their A-acetyl derivatives in the rat. Toxicol, appl. Pharmacol., 102, 142-150... 

SAMPLE SOLUTION (a) Because direct nitration of aniline is not a practical reaction, the amino group must first be protected as its A/-acetyl derivative. 

A common example that has been isolated from many plant polysaccharides is 2-0-(4-0-methyl-a-D-glucopyranosyluronic acid-D-xylose (64). Hyalobiouronic acid, [2-amino-2-deoxy-3-0-(/f-D-glucopyranosyluronic acid)-D-glucose] (65), whose A-acetyl derivative is the repeating unit of... 

By analogy with the synthesis of /V-acetylneuraminic acid,63 di-A-acetyl derivatives of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids could be obtained by condensation of 2,4-diacetamido-2,4,6-trideoxyhexoses with oxaloacetic acid under basic conditions. Four chiral centers in the C precursors, C-2 C-5, correspond to the centers C-5-C-8 in the target C9 products, and the fifth asymmetric center, C-4, is formed upon condensation. At present, derivatives of twelve 2,4-diamino-2,4,6-trideoxy-hexoses with the d-gluco, o-manno, L-allo, r>-galacto, D- and L-altro, D- and L-talo, D- and l-gulo, D- and L-ido configurations have been prepared by multistep chemical syntheses.11,17,18,64,65... 

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