7- Aminodesacetoxycephalosporanic acid

Cephalosporins are a class of antibiotic produced via the intermediate 7-aminocephalos-poranic acid (7-ACA), or 7-aminodesacetoxycephalosporanic acid (7-ADCA). Directed evolution has been used to improve the activity of cephalosporin acylases to produce these intermediates from adipyl-7-ACA or cephalosporin C [68]. Using site-directed saturation mutagenesis and a selection system whereby the E. coli host is dependent on leucine liberated from derivatives of the cephalosporin side-chains, a mutant was found that increased the catalytic efficiency toward adipyl-7-ADCA by 36-fold. 

Semi-synthetic penicillins are accessed from 6-aminopenicillanic acid, (6-APA), derived from fermented penicillin G. Starting materials for semi-synthetic cephalosporins are either 7-aminodesacetoxycephalosporanic acid (7-ADCA), which is also derived from penicillin G or 7-aminocephalosporanic acid (7-ACA), derived from fermented cephalosporin C (Scheme 1.10). These three key building blocks are produced in thousands of tonnes annually worldwide. The relatively labile nature of these molecules has encouraged the development of mild biocatalytic methods for selective hydrolysis and attachment of side chains. 

Other amino acids, and some antibiotics, especially the conversion of 6-amino-penicillanic acid (APA) to 7-aminodesacetoxycephalosporanic acid (ADCA), acrylamide, aspartame, citric acid, and niacinamide. 

MJ Conder, PC McAda, JA Rambosek. Recombinant expandase bioprocess for preparing 7-aminodesacetoxycephalosporanic acid (7-ADCA). U.S. Patent 5,318,896, 1994. 

Simultaneous 7-aminocephalorospanic acid, 7-aminodesacetoxycephalosporanic acid, ce-fazolin, cephaloridine, cephalothin, cephradine... 

Chemferm is one of among several companies which apply penicillin acylase for the kinetically controlled industrial synthesis of semisynthetic antibiotics in aqueous environments (Scheme 37) [109-111]. Ampicillin (119) and amoxicillin (120) can be obtained by the enzyme-catalyzed condensation of 6-aminopenicillic acid (6-APA, 117) with the amide or ester of D-(-)-4-hydrox-yphenylglycine and D-(-)-phenylglycine, respectively. In a similar way, cephalexin (121) can be obtained by reaction of D-(-)-phenylglycine with 7-aminodesacetoxycephalosporanic acid (7-ADCA, 118). Penicillin acylase from diverse microbial strains such as E. colU Klyveromyces citrophiluy and Bacillus megabacterium was successfully applied for this transformation and was used in its immobilized form based on a gelatin carrier. The immobilization allows an easy separation from the reaction medium and the reuse of the enzyme for at least 50 cycles. Impressive characteristics of this transformation are yields >90%, a selectivity of >95%, and an optical purity of >99% ee. The industrial manufacture takes place in repetitive batch reactors at many locations worldwide with an annual production volume of 2,000 t. 

The starting material for the most important semi-synthetic )3-lactam antibiotics is penicillin G or adipoyl-7-aminodesacetoxycephalosporanic acid. From these, ampicUlin, amoxicillin, cephalexin and cefadroxU are obtained in considerable tonnage. [48] The essential intermediates for this are 6-aminopenicillanic acid or 7-aminodesacetoxycephalosporanic acid. 

Structure-activity relationships for a group of semi-synthetic phenyl-glycine derivatives of 7-aminodesacetoxycephalosporanic acids, including cephalexin, have been compared with those of the corresponding cephalosporins. ... 

With the OPLC-System, described before (19), cephalosporin C, 7-aminocephalosporanic acid, 7-aminodesacetoxycephalosporanic acid and cefalotin can be separated. The values are 0.95,0.88, 0.68 and 0.26, respectively. The layers of silica, coated with anunonium tungstophosphate, mentioned before can also be used for the separation of cefalexin, cefaloglycin, cephalosporin C and 7-aminocephalosporanic acid. With solvents IM and 4M NH4NO3 for A the values are 0.07,0.11, 0.42,0.74 and 0.24,0.33,0.74,0.86, respectively. For B and IM NH4NO3 0.52,0.69,0.90 and 0.99 were found. 

To a 1 liter flask containing dimethylformamide at 0°C, was added 24.8 g sodium N-(2-methoxycarbonyl-l-methylvinyl)-D-a-phenylglycine (prepared from sodium D-a-phenylglycine and methyl acetoacetate). The mixture was cooled to -40°C and methyl chloroformate (7.5 ml) and dimethylbenzylamine (0.26 ml) added. After stirring for 25 minutes, p-nitrobenzyl 7-aminodesacetoxycephalosporanate (32.8 g) in the form of its hydrochloride salt was added, followed by triethylamine (12.1 ml) and dimethylformamide (140 ml) over a period of 20 minutes. The reaction mixture was stirred for 2 hours at -25°C to -35°C, then warmed to 0°C and water (32 ml) added. To the resultant solution, hydrochloric acid (54 ml) was added followed by zinc (21.8 g) in portions over a period of 5 minutes, the temperature being maintained at 5°C to 10°C. Further hydrochloric acid (35 ml) was added and the solution stirred at 15°C to 20°C for 7 hours. 

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