In terms of the spectrum of antimicrobial action, oxacillin is analogous to benzylpenicillin. However, it combines the resistance to penicillinase with durability in an acidic medium, which allows it to be used not only intramuscularly, but also orally. It is used for infections caused by penicillinase-producing staphylococci that are resistant to benzyl- and Phenoxymethylpenicillins (septicemia, pneumonia, abscesses, empyemia, osteomyelitis, infected burns, infected wounds, and others). Synonyms of this drug are cryptocillin, liucipen, optocillin, totocillin, and others.

Cloxacillin: Cloxacillin, [2S-(2a,5a,6ß)]-3,3-dimethyl-7-oxo-6-[(5-methyl-3-(o-chlor-phenyl)-4-isoxazolcarboxamido)]-4-thia-1-azabicyclo[3.2.0]-heptan-2-carboxylic acid (, is synthesized from o-chlorobenzaldehyde by the scheme described above [21-23,25].

In terms of mechanism of action and indications for use, it is analogous to oxacillin. Synonyms of this drug are ampiclox, orbenin, totaclox, tegopen, and others.

Dicloxacillin: Dicloxacillin, [2S-(2a,5a,6ß)]-3,3-dimethyl-7-oxo-6-[(5-methyl-3-(2,6-dichlorophenyl)-4-isoxazolcarboxamido)]-4-thia-1-azabicyclo[3.2.0]-heptan-2-carboxylic acid (, is also synthesized by the scheme described above using 2,6-dichloroben-zaldehyde as the starting substance [26-28].

In terms of mechanism of action, antibacterial spectrum, and indications for use, it is essentially no different than oxacillin and cloxacillin. Synonyms of this drug are diclocil, novapen, diclex, and others.

The following type of semisynthetic penicillins that should be considered are those in which amino acids, mainly a-aminophenylacetic or p-oxy-a-amino-phenylacetic acids, act as the acyl radical (ampicillin, amoxacillin).

The antimicrobial spectrum of aminopenicillins is similar to penicillin G, with the exception that they also act on a number of Gram-negative microorganisms. Both aminopenicillins are destroyed by staphylococcus penicillinase.

Ampicillin: Ampicillin, [2S-[2a,5a,6^(S)]]-3,3-dimethyl-7-oxo-6-(2-amino-2-pheny-lacetamido)-4-thia-azabicylco[3.2.0]-heptan-2-carboxylic acid (, is synthesized in various ways using different methods of protection of amino group in the starting phenylglycine. One of the most widely used methods uses the benzyl chloroformate. Reacting this with phenylglycine initially forms benzyloxycarbonylphenylglycine ( Treating this with ethyl chloroformate in the presence of triethylamine gives a mixed anhydride ( with a protected amino group that easily reacts with 6-APA

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