Benzylpenicillin isolation

Semisynthetic. In 1959, scientists at Beecham Researeh Laboratories sueceeded in isolating the penicillin nucleus, 6-aminopenicillanie aeid (6-APA Fig. 5.1 A R represents H). During the commercial production of benzylpenicillin, phenylacetic (phenylethanoic) acid (C6H5.CH2.COOH) is added to the medium in whieh the Penicillium mould is growing (see Chapter 7). This substance is a precursor of the side... 

About a decade later, a group of researchers at Oxford University isolated a crude substance made up of a few low-molecular substances, which were penicillins (F, G, K, O, V, X). Penicillin G (benzylpenicillin), the most active of these, was suggested for clinical trials in 1941. 

Sulbactam sodium is semi-synthetic antibiotic of penicillinic group. Start material for it s synthesis is 6-aminopenicillanic acid. First 6-aminopenicillanic acid was isolated in 1957 year from benzylpenicilline as resalt of treating of it by penicillinaze. Benzylpenicilline is produced by microorganism of genus Streptomyces. 

Penicillin (or benzylpenicillin) (32a) (R = CH2Ph) was first dicovered by Sir Alexander Fleming in 1929, who isolated the antibiotic from the fungal strain Penicillium notatum (see Introduction, p. 4). Penicillin is valuable to combat bacterial infections in man and animals. It was first manufactured commercially in 1945 and the first semisynthetic penicillins were introduced in 1954. The penicillins (32) have a common structural feature, namely a p-lactam ring fused to the... 

In attempts to synthesize the oxazolone-thiazolidine of formula 2, by condensing the dimethylcysteine with the appropriate oxazolone, it was noted that the reaction products always showed a very low antibiotic activity though they had properties similar to penicillin. However, at first all attempts to concentrate the activity by various fractionation procedures, including chromatography, failed and it was doubted in many circles whether or not the activity could really be due to penicillin. This uncertainty was resolved by du Vigneaud and co-workers (S) who employed the method of countercurrent distribution (see Chapter I), and were able to isolate a crystalline sodium salt from the mixture. This salt had full antibiotic activity and was identical in every respect with naturally-occurring benzylpenicillin. The synthetic acid was present in the reaction mixture at a concentration of only about 0.1%. 

Fig. 8.1. Per cent of resistant strains of staphylococci (A) isolated from patients (a), environement (b), and personnel (c), and monthly uses of antibiotics (B, in hundreds of grams) in a surgical clinic. PNC — benzylpenicillin, STM — streptomycin, CTC — chlorotetracycline, ERY — erythromycin, CHL — chloramphenicol (modified...

In 1929, Fleming discovered that the mould Penicillium notatum inhibits the growth of bacteria. In 1941 Florey and Chain succeeded in isolating the active agent, known as penicillin, in the form of its sodium salt. The structural elucidation was achieved by chemical degradation and was confirmed in 1945 by X-ray analysis of penicillin G (benzylpenicillin). The structures were shown to be (3/S,5i ,6/ )-6-(acylamino)-2,2-dimethyl-7-oxopenam-3-carboxylic acids ... 

Isolated cases of increased prothrombin times and/or bleeding have been seen in patients given amoxicillin (with or without cla-vulanic acid) intravenous benzylpenicillin, phenedcillin or ta-lampicillin. An increased risk of over-anticoagulation was seen with amoxicillin with or without clavulanic acid in cohort studies, but not flucloxacillin. There is also some evidence that phe-noxymethylpenicillin (penicillin V) does not interact. 

The polymers isolated from ampicillin and benzylpenicillin solutions have further been shown to give wheal and flare reactions in a number of penicillin allergic patients, all of whom have given skin reactions also to a penicilloyl-polylysine conjugate (JuHLiN et al. 1977). Finally, a limited clinical study by Parker and Richmond (1976) has indicated that the use of so-called polymer-free ampicillin may reduce the incidence of certain exanthematic adverse reactions to ampicillin preparations. 

Polymerization of benzylpenicillin has been described by several authors (Batchelor et al. 1967 Stewart 1967 a de Weck et al. 1968 Butcher and Stewart 1969, 1970 Dewdney et al. 1971 Smith et al. 1971 Smith and Marshall 1971 Bungaard and Larsen 1977). Polymerization probably involves hydrolysis of the beta-lactam ring to form penicilloic acid, followed by acylation of the exposed thiazolidine nitrogen by another intact penicillin molecule or a benzyl-penicillenic acid derivative (Stewart 1973 Smith and Marshall 1971 Schneider and de Weck, 1970) (Fig. 8) Such polymers have been isolated by Sephadex gel chromatography (Smith et al. 1971) or by high-pressure liquid chromatography (Bundgaard 1977 b). Polymers have been isolated also from other semisynthetic penicillins such as hetacillin and carbenicillin (Smith et al. 1971), methicillin and pheneticillin (Butcher and Stewart 1970). 

Aminopenicillanic acid (6 APS) is an important precursor for the organic synthesis of new P. The compound itself has no antibiotic activity it is isolated as a fermentation product from cultures of Pen-cillium chrysogenum, or prepared by the enzymatic hydrolysis of benzylpenicillin. Thousands of new P. have been prepared by the acylation of 6 APS, but only a few of these are therapeutically useful, e.g Penicillin V is relatively stable to acid and is not hydrolysed in the stomach, so that it may be administered in tablet form Ampicillin (the aminophenyl-acetyl derivative of 6 APS), has a wider spectrum of activity than most other R, including activity against various Gram-negative bacteria (Typhus, E. coli, etc.). 

An interesting use of mixed radioisotope and stable isotope labelling was demonstrated when the formation of benzylpenicillin by Penicillium chryso-genum in the presence of L- and D-[3- C, N, S]cystine was studied. The penicillin isolated contained the three labels in their proportions in the precursor when L-cystine had been added to the fermentation medium. It was concluded that cystine was a direct precursor of penicillin, probably after reduction to cysteine [215]. 

As noted in the Chapter 5 Lagniappe, more than half of all new drug candidates come either directly or indirectly from natural products. All four natural products shown in the introduction to this chapter, for instance, are used as drugs morphine from the opium poppy, prostaglandin Ej from sheep prostate glands, erythromycin A from a Strepto-myces erythreus bacterium cultured from a Philippine soil sample, and benzylpenicillin from Penicillium nota-tum. Still other examples include rapamycin (Figure 25.15), an immunosuppressant isolated from a Strepto-myceshygroscopicus bacterium first found in a soil sample from Easter Island (Rapa Nui), and paclitaxel (Taxol),... 

In a double-labelled experiment it was shown that when cystine was fed to P. chrysogenum the isotope ratio of the starting material was retained unchanged in the isolated benzylpenicillin. This demonstrated that cystine (rather than penicillamine) was the source of the thiazolidine sulphur atom. Further evidence on the origin of the penicillin sulphur atom was provided by Stevens etal, 212) who showed that the label from p S]-cysteine was better incorporated into benzylpenicillin than label from P S]-sulphate. In competition experiments it was shown that L-cysteine or L-cystine were utilised in preference to p S]-sulphate, whereas D-cysteine and DL-penicillamine had no effect on the incorporation of label from sulphate into benzylpenicillin. 

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