Acetyl adenylate and

Resistance to this type of antibiotic is usually mediated by acetylation, adenylation and phosphorylation mostly in rings A and B causing thus lowered or abolished antibiotic affinity to the RNA [87]. 

The second group of compounds studied by Jencks et al. were acyl phosphates (Table 19.2). The acetyl phosphate dianion, which is the predominant ionic species at neutral pH, has a carbonyl band at 1713 cm Acylated phosphate monoesters, such as acetyl adenylate and acetyl phenyl phosphate absorb at higher frequencies of 1737 to 1747 cm and the structurally similar acetyl phosphate monoanion absorbs... 

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