Answer to Question #150661 in Organic Chemistry for fatima

Question

Describe the structural features of monobactams, how it retains its activity?

Answer 1

Monobactams are basically such type of antibiotics in which the following features are found.

1. It is monocyclic and contains β-lactam ring
2. Here the β-lactam ring is not fused to the adjacent ring, just like most of other β-lactams
3. It generally contains a -SO₃H group
4. They are only effective against aerobic gram-negative bacteria

The representative structure of Monobactams is shown bellow

As the monobactam nucleus exhibits weak antibacterial activity, molecular substitution around the central nucleus is essential to understand the antibacterial potential of these molecules. When we do side chain substitution of the monobactam nucleus, then it shows primarily Gram-positive, primarily Gram-negative or broad-spectrum activity. The most prominent gain in anti-bacterial activity is observed when an aminothiazoleoxime side chain as the 3-acyl substituent is introduced. Substitution at the 4-position of the monocyclic ring although capable of producing dramatic changes in biological activity which is highly unpredictable. In the SO3-activated molecules 4-substitution is essential for beta-lactamase stability. The 'activating' group on the beta-lactam nitrogen is responsible for the activation of the beta-lactam ring and it can be varied quite widely while retaining high intrinsic activity.