10 Questions
What is crucial to the mechanism of b-lactam antibiotics?
The b-lactam ring
What is important for binding in b-lactam antibiotics?
The carboxylic acid at position 4
What is important for increasing ring strain in b-lactam antibiotics?
The bicyclic system
What is a possible modification of b-lactam antibiotics?
7-Acylamino side chain
What is important to the mechanism of b-lactam antibiotics?
The acetoxy substituent
Why is cefalexin orally administered?
Because of its hydrophilic amino group
What is the significance of the methyl group at position 3 in cefalexin?
It is a poor leaving group
What is the role of the hydrophilic amino group in cefalexin?
It compensates for the loss of activity due to the methyl group
What is the effect of the methyl group on the antibiotic's activity?
It reduces the activity
What is the significance of the side chain in cefalexin?
It contains a hydrophilic amino group
Study Notes
Cephalosporin Mechanism
- The β-lactam ring is crucial to the mechanism of cephalosporins.
- The carboxylic acid at position 4 is essential for effective binding.
- The bicyclic system increases ring strain, contributing to the mechanism.
- Stereochemistry plays a significant role in the mechanism of cephalosporins.
- The acetoxy substituent is vital to the mechanism.
Possible Modifications
- 7-Acylamino side chain can be modified.
- The 3-Acetoxymethyl side chain is another possible modification.
- Substitution at C-7 is a potential modification.
Cefalexin Structure and Activity
- The methyl group at position 3 is not a good leaving group.
- The presence of a methyl group at position 3 compromises the activity of cefalexin.
- However, the methyl group enhances oral absorption of cefalexin.
Cefalexin Administration
- Cefalexin can be administered orally due to the presence of the methyl group.
Side Chain Features
- The presence of a hydrophilic amino group at the alpha-carbon of the side chain helps to compensate for the loss of activity caused by the methyl group.
- The hydrophilic amino group improves the activity of cefalexin despite the negative effect of the methyl group.
This quiz covers the structure and mechanism of cephalosporin antibiotics, including the importance of the b-lactam ring, carboxylic acid, and stereochemistry. It also explores possible modifications to the antibiotic structure.
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