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BIOPHARMACEUTICALS BIOCHEMISTRY AND BIOTECHNOLOGY - PART 2

Điều chỉnh xuống của các phản ứng pH 4.3 kết quả về lượng mưa của các axit kết quả vòng 6-aminopenicillanic, mà sau đó có thể dễ dàng thu hoạch. Sidechains cuốn tiểu thuyết sau đó có thể được đính kèm, sinh bán tổng hợp penicillin. Ví dụ thứ hai bao gồm phenethicillin, propicillin và oxacillin. | PHARMACEUTICALS BIOLOGICS AND BIOPHARMACEUTICALS 37 Figure 1.16. Chemical structure of the antibiotic tetracycline. Other members of the tetracycline family see also Table 1.18 also display this characteristic 4-ring structure penicillin acylase . Downward adjustment of the reaction pH to 4.3 results in precipitation of the resultant 6-aminopenicillanic acid ring which can then be easily harvested. Novel sidechains can subsequently be attached yielding semi-synthetic penicillins. Examples of the latter include phenethicillin propicillin and oxacillin. Some semi-synthetic penicillins are effective against bacterial pathogens that have become resistant to natural penicillins. Others are acidstable allowing their oral administration. Cephalosporins display an antibiotic mechanism of action identical to that of the penicillins. Cephalosporin C Figure 1.14 is the prototypic natural cephalosporin and is produced by the fungus Cephalosporium acremonium. Most other members of this family are semi-synthetic derivatives of cephalosporin C. Chemical modification normally targets side-chains at position 3 the acetoxymethyl group or 7 derived from D-a-aminoadipic acid . Tetracyclines are a family of antibiotics which display a characteristic 4-fused-core ring structure Figure 1.16 . They exhibit broad antimicrobial activity and induce their effect by inhibiting protein synthesis in sensitive microorganisms. Chlortetracycline was the first member of this family to be discovered in 1948 . Penicillin G and streptomycin were the only antibiotics in use at that time and chlortetracycline was the first antibiotic employed therapeutically that retained its antimicrobial properties upon oral administration. Since then a number of additional tetracyclines have been discovered all produced by various strains of Streptomyces and a variety of semi-synthetic derivatives have also been prepared Table 1.18 . Tetracyclines gained widespread medical use due to their broad spectrum of activity .