What Comprises a Penicillin Structure?
Several naturally occurring penicillins have now been isolated, and numerous derivatives of these substances have been synthetically produced. All have structures containing a four-membered β-lactam ring (4 membered cyclic amide) fused with a five-membered thiozolidine ring. The carbon atom of the amide on the β-lactam ring can be bonded to any substituent, called the 'R-group'.
Penicillins as well as cephalosporins are called beta-lactam antibiotics and are characterized by three fundamental structural requirements: the fused beta-lactam structure (shown in the blue and red rings, a free carboxyl acid group (shown in red bottom right Figure1.1), and one or more substituted amino acid side chains (shown in black). The lactam structure can also be viewed as the covalent bonding of pieces of two amino acids - cysteine (blue) and valine (red). Fig. 1.1: Penicillin – Beta Lactam Structure
In terms of functional groups, the penicillin has 4 different functional groups: namely, carboxylic group, amide group, methyl group, and thioether group.
Penicillin consists of many different functional groups but as a group of drugs the difference lies in the group that is placed after the unified functional group called a penam. The penam is a characteristic feature of the Penicillin family of drugs. A penam group contains a ketone with one R group consisting of a secondary amine. This secondary amine bridges the ketone to the Beta-lactam ring that is a four membered ring with nitrogen bonded to a carbonyl group. That ring is attached to another ring that is considered a cyclopentyl-thioether that is a cyclic ether with a sulfur atom instead of an oxygen atom. The last functional group is the Carboxylic acid, which is a carbonyl group bonded to an alcohol group. The beta-lactam ring and the cyclic thioether are, collectively, also considered a bicyclic compound.
One can see that the lactam ring is highly strained: four near 90o angles create an instability that can
Penicillins as well as cephalosporins are called beta-lactam antibiotics and are characterized by three fundamental structural requirements: the fused beta-lactam structure (shown in the blue and red rings, a free carboxyl acid group (shown in red bottom right Figure1.1), and one or more substituted amino acid side chains (shown in black). The lactam structure can also be viewed as the covalent bonding of pieces of two amino acids - cysteine (blue) and valine (red). Fig. 1.1: Penicillin – Beta Lactam Structure
In terms of functional groups, the penicillin has 4 different functional groups: namely, carboxylic group, amide group, methyl group, and thioether group.
Penicillin consists of many different functional groups but as a group of drugs the difference lies in the group that is placed after the unified functional group called a penam. The penam is a characteristic feature of the Penicillin family of drugs. A penam group contains a ketone with one R group consisting of a secondary amine. This secondary amine bridges the ketone to the Beta-lactam ring that is a four membered ring with nitrogen bonded to a carbonyl group. That ring is attached to another ring that is considered a cyclopentyl-thioether that is a cyclic ether with a sulfur atom instead of an oxygen atom. The last functional group is the Carboxylic acid, which is a carbonyl group bonded to an alcohol group. The beta-lactam ring and the cyclic thioether are, collectively, also considered a bicyclic compound.
One can see that the lactam ring is highly strained: four near 90o angles create an instability that can