A-acetyl groups

Sulfaguanidine is prepared by condensation of Ai-acetylsulfanilyl chloride with guanidine ia presence of alkali. The A/ -acetyl group is removed by acid or alkaline hydrolysis. 

To overcome this, the A -acetyl group is reduced with lithium aluminum hydride. The resulting basic enamine then reacts extremely rapidly and selectively with peracid. The derived epoxide is hydrolyzed very easily with alkali during the workup. 

Amide resonance within the A-acetyl group competes with delocalization of the nitrogen lone pair into the ring. 

A -acetyl groups attached to the aniline have been shown to withstand the Conrad-Limpach reaction. Phenols and alcohols also survived unless in proximity to a reactive center. Jaroszewski reported the formation of 64 by reaction of aniline 63 with ethyl acetoacetate (5). Cyclization under thermal conditions in paraffin gave a mixture of quinolone 65 and quinoline 66. 

Nitrile 241 was reduced to the amine 242 with Red-Al in morpholine at —40 °C. However aluminium hydrides are mostly unsuitable if there is an A-acetyl group that is required to be conserved and this is discussed further in Section 8.06.8. Also, 240 could be prepared from the ester 243 by reaction with ammonia <1982AP538>. 

A-acetyl group. Compare these intermediates with those in the salvage pathway (fig. 22.2a) and propose a reason for the acetyl groups. 

The A-acetyl groups in the de novo pathway prevent the spontaneous cyclization of the semialdehyde intermediate. 

A role of the 5-A-acyl group of pseudaminic acid in serospecificity was demonstrated in studies of P. aeruginosa serogroup 07 strains, which could be divided into three subgroups 07a,7b,7c, 07a,7b,7d, and 07a,7d (Section II.2, Fig. 3). It was concluded that epitopes 07c and 07d are linked to the 5-TV-[(R)-3-hydroxybutanoyl] and 5-A-acetyl group, respectively.23... 

Assignment of the signals for C02H of the sugar and CO of the A -acetyl groups could be interchanged. 

When anomeric acetate moiety is GlcNAc it is desirable to protect the A-acetyl group (100). 

O-Alkylation of imidazo[4,5-h]pyridin-2-ones (110) sometimes occurs on treatment with alkyl halides or diazomethane <78H(iO)24l, 78JHC937), and one instance of O- as well as A-acetylation as in (111) has been reported (the position of the A-acetyl group was not firmly established) (59JOC1455). 

Regenerate the amino acids by protonation of the carboxylate salt and hydrolysis of the A/-acetyl group. 

Replacement of the A -acetyl group of GlcNAc with an electron-withdrawing A-aUyloxy-carbonyl (Aloe) [103], A -trichloroethoxycarbonyl (Troc) [87,104-106] or A-dithiasuccinoyl (Dts)... 

Interestingly, the comparison of the X-ray crystal structures of the complexes of influenza A neuraminidase with zanamivir 28 and BANA 113 42 revealed that, whUe the carboxylate and A-acetyl groups occupy the same subsites, the guanidino functionalities interact with the enzyme in different ways (Figure 16.14) [9Id]. 

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