Chemistry Reference
In-Depth Information
R
H
N
CH
3
C
H
H
O
H
N
O
CH
3
CO
2
H
Acyl-
D
-Ala-
D
-Ala
R
HH
S
H
N
C
CH
3
O
N
CH
3
CO
2
H
O
Penicillin
R
HH
S
H
N
C
O
N
CH
3
O
CO
2
H
Cephalosporin
Figure 4.10
The structures of
D
-alanine-
D
-alanine dipeptide, penicillin and
cephalosporin.
the drug. A large number of hospital-acquired infections are now resistant
to treatment by penicillin, including the notorious MRSA or meticillin
(formerly methicillin) resistant
Staphylococcus aureus.
This 'super bug'
produces an enzyme, b-lactamase, which hydrolyses the b-lactam ring and
inactivates the penicillin. Organisms which are resistant to treatment with
antibiotics pose one of the greatest threats to modern pharmacy and
medicine. At the moment, drugs such as the glycopeptide derivatives
vancomycin and teicoplanin are reserved for use against difficult infections,
