Penicillin are as group of medicines which produced by different species and strains of Penicillium. They are widely used against bacterial infections caused by Staphylococcus and Streptococcus.

All medicines in this group have a common core called 6-aminopenia silanic acid. 6- Aminopenia silanic acid (6 APA), also called beta-lactam core, is the main intermediate in production of beta-lactam, which is formed by reaction of L-cysteine and of D-Valine 1:1.

6- Amino-silanic acid as a penicillanic acid derivative has a substitution in its 6R-amino position.