Cephamycin isolation

Occurrence, Fermentation, and Biosynthesis. Although a large number of Streptomjces species have been shown to produce carbapenems, only S. cattkja (2) and S. penemfaciens (11) have been reported to give thienamycin (2). Generally the antibiotics occur as a mixture of analogues or isomers and are often co-produced with penicillin N and cephamycin C. Yields are low compared to other P-lactams produced by streptomycetes, and titres are of the order of 1—20 p-g sohdusmL despite, in many cases, a great deal of effort on the optimization of the media and fermentation conditions. The rather poor stabiUty of the compounds also contributes to a low recovery in the isolation procedures. The fermentation and isolation processes for thienamycin and the olivanic acids has been reviewed in some detail (12). 

At present all of the cephalosporins ate manufactured from one of four P-lactams, cephalosporin C (2), penicillin V [87-08-17, penicillin G [113-98-4] and cephamycin C (8), which ate all produced in commercial quantities by fermentation (87). The manufacturing process consists of three steps fermentation, isolation, and chemical modification. 

Isolation. Isolation procedures rely primarily on solubiHty, adsorption, and ionic characteristics of the P-lactam antibiotic to separate it from the large number of other components present in the fermentation mixture. The penicillins ate monobasic catboxyHc acids which lend themselves to solvent extraction techniques (154). Pencillin V, because of its improved acid stabiHty over other penicillins, can be precipitated dkecdy from broth filtrates by addition of dilute sulfuric acid (154,156). The separation process for cephalosporin C is more complex because the amphoteric nature of cephalosporin C precludes dkect extraction into organic solvents. This antibiotic is isolated through the use of a combination of ion-exchange and precipitation procedures (157). The use of neutral, macroporous resins such as XAD-2 or XAD-4, allows for a more rapid elimination of impurities in the initial steps of the isolation (158). The isolation procedure for cephamycin C also involves a series of ion exchange treatments (103). 

Table 8.22. IN VITRO ACTIVITY OF CEPHAMYCIN C AGAINST SOME CEPHALOSPORIN-RESISTANT CLINICALLY ISOLATED CULTURES [199]...

One approach has been to modify the structure of the yS-lactam antibiotic so as to increase its stability and thus confer resistance to yS-lactamases, whilst retaining its inhibitory activity against transpeptidases. This was achieved by introducing sterically crowded 6-acyl substituents, as in methicillin (1) and the isoxazolyl penicillins (2) and (3) [20], or by the introduction of a methoxy substituent to the a-face of the -lactam, as in cefoxitin (9) [21] and temocillin (11) [22]. The two latter compounds were a direct result of the discovery of the y5-lactamase stable cephamycins (10), isolated by fermentation of Streptomyces in 1970 by Merck and Lilly [23]. 

Cephamyclns - At present, the standard cephamycin is cefoxitin (14). A review lists the isolated natural variants as well as the various methods for the 7a-methoxylation of cephalosporins, SK F 73678 (15),CS-1170 (16) and SQ 14,359 (17) have been studied in the laboratory.- Basically... 

The search continues for the ideal beta-lactam antibiotic, and numerous esoteric substances have been isolated from natural sources or have been synthesised during the past 15 years. These include the penems, carbapen-ems, cephamycins, monobactams, etc. The penems are wholly synthetic and from a clinical viewpoint have not been successful, while more success has been obtained with the carbapenems, which include the natural product thienamycin (from Streptomyces cattleya) and the analogues imipenem and meropenem. These carbapenems have a remarkable spectrum of antibacterial activity with a very high activity against pseudomonads. Thienamycin is relatively unstable, but the addition of a formamidine group to produce... 

Cephamydns, A family of fJ-lactam antibiotics produced by various Streptomyces species. Detection and production Stapley et at.. Antimicrvb. Ag. Chemother. 2, 122 (1972). Chemical characterization Miller et al, ibid. 132. Cephamycins A, B, and C have been isolated, tha latter being identical to a Streptomyces clavullgerus metabolite Nagarajan et ah. J. Am. Chem. Soc. 93, 2308 (1971). Structures Albers -Sehoenberg et ah, Tetrahedron Letters 1972, 2911- Antibacterial activity studies Miller et ah, dmimi-crob. Ag. Chemother. 2, 281, 287 (1972) Daoust et al. ibid. 3, 254 (1973). Review of syntheses T. Hiraoka et ah. Heterocycles 8, 719 (1977). 

The search at the Lilly Research Laboratories for new lactams of natural origin has led to the isolation of several new cephems bearing substituents other than acetoxy at C-10. During this programme, carbamoyloxymethyl-cephems (2361) and (236b) cephamycin C were isolated [198]. Other members of the cephamycin family (236g,h) [199,200] and (236i) [201] were found in different species of Streptomyces (see also ref. 183). 

In 1972, cephamycin C, a member of a family of antibiotics structurally closesy related to cephalosporin C, was isolated. The cephamycins were produced in submerged fermentation in a wide variety of media by one or more of eight different species of Streptomyces, including Streptomyces lactamdurans. To cephamycin C was assigned the structure 82 [135]. Cephamycin C and other members of this family... 

The fermentation of S. clavuligerus and S. lipmanii for cephamycin C production is described in detail by Nagarajan (1973). The following procedures are those used in the isolation of cephamycin C from 5. lactamdurans NRRL 3802. 

Stapley et al. (1972) reported on the isolation of cephamycins A and B from Streptomyces griseus MA-2837. Antibiotic production was monitored using a disk plate diffusion assay with P. vulgaris MB-838 or V. percolans ATCC 2461 (Fig. 1). 

The isolation of cephamycin C from Streptomyces wadayamensis and S. jumonjinensis is described by workers at Fujisawa (Arai et al., 1975). Some typical properties of cephamycin C are shown in Table II. 

Fig. 3. Isolation of cephamycin C. Data from Christensen and Firestone (1973).

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