Chemistry Reference
In-Depth Information
which suggests the molecule contains an odd number of nitrogens
(1, 3, 5, etc). This is called the 'nitrogen rule' and arises because
most common atoms with an even atomic mass form an even
number of covalent bonds, while an odd mass suggests an odd
number of bonds. Nitrogen is unusual in that it has an atomic
mass of 14 and a valency of 3.
(a)
The benzylic positions and, in particular, the phenol are
likely to undergo oxidation on storage (Figure 11.10).
A8.1
(b)
The groups susceptible to hydrolysis are the amide, the
cyclic ester (a lactone), the glycoside and the carbamate
(Figure 11.10).
Amide
Phenol
OH
OH
H
N
Glycoside
O
O
O
O
CH
3
CH
3
Cyclic
ester
Benzylic position
H
3
C
CH
3
O
O
OH
O
O
Benzylic position
H
2
N
Carbamate
Figure 11.10
The structure of novobiocin.
(c)
Novobiocin should be stored in an airtight container and
protected from light.
(d)
The drug must be water soluble when administered in an
infusion. This is achieved by forming the sodium salt of
novobiocin. As this is the salt of a weak acid and a strong
base, aqueous solutions are alkaline by partial hydrolysis
(revise Chapter 1 if you do not follow this!). When the drug
is added to a 5% Dextrose Infusion (pH 3.5-6.5), the pH
of the solution is sufficiently low to precipitate the water-
insoluble free acid of novobiocin from solution of the salt,
turning the solution cloudy. If this precipitation occurs in
