2. STEROLS: STRUCTURE AND DISTRIBUTION
109
group, CH 2 =, in the side chain could be detected only by ozonolysis,
a method wasteful of precious material. Today its presence is readily
recognized by its absorption bands in the infrared spectrum (see below). The same holds true for many other double bonds in the molecule.
A particularly lucid treatment of the significance and practical application of ultraviolet absorption spectroscopy is found in Fieser and Fieser's
excellent monograph on steroids (14), and that of infrared spectroscopy
in Cole's informative review (16).
At the time of the discovery of most of the natural sterols not only
were their structures unknown, but often also their correct empirical
formulas and the degree of their uniformity. To facilitate discussion of
the occurrence of such sterols, they were generally given names relating
them to the organism from which they had first been derived. These are
names of convenience, and any confusion they will cause will be but
temporary. Once the structures of such sterols have been fully established, such names should be discarded and be replaced by others
denoting their chemical structure and their relation to such well-known
sterols as cholesterol. Long-accepted names will probably always be
retained. Thus it appears unlikely that the short name ergosterol will be
replaced by the more instructive but rather cumbersome 3ß-hydroxy-24amethyl-A
5 '
7 '
22 -cholestatriene or even the shorter 24a-methyl-7,22-bisdehydrocholesterol. The host of other sterols substituted by alkyl groups
at C-24 are best referred to as derivatives of cholesterol as was suggested by the author some time ago (17). The organic chemist knows
that the occasional, Babylonian confusion of names for natural products
will never be of long duration and will terminate once the structures
of the compounds have been ascertained. In contrast, no end appears
to be in sight to the exasperating confusion caused by the multiplicity
of names for biological species and the lack of agreement in their
application.
B. STRUCTURES
Until a few years ago the term sterols embraced only those steroids
that differ from cholesterol only in the number and position of double
bonds in the rings or the side chain, or the attachment to the side chain
of substituents such as alkyl groups at C-24. With the recognition of
the structural and biosynthetic connections between sterols and triterpenoids such "methylsterols" as lanosterol and agnosterol (VI and VII;
R = B) must also be included among the natural sterols. At present,
however, very little is known about the occurrence of methylsterols in
animal tissues or products other than wool grease (lanolin).
The sterols which are known or suspected to occur in animals may
109
group, CH 2 =, in the side chain could be detected only by ozonolysis,
a method wasteful of precious material. Today its presence is readily
recognized by its absorption bands in the infrared spectrum (see below). The same holds true for many other double bonds in the molecule.
A particularly lucid treatment of the significance and practical application of ultraviolet absorption spectroscopy is found in Fieser and Fieser's
excellent monograph on steroids (14), and that of infrared spectroscopy
in Cole's informative review (16).
At the time of the discovery of most of the natural sterols not only
were their structures unknown, but often also their correct empirical
formulas and the degree of their uniformity. To facilitate discussion of
the occurrence of such sterols, they were generally given names relating
them to the organism from which they had first been derived. These are
names of convenience, and any confusion they will cause will be but
temporary. Once the structures of such sterols have been fully established, such names should be discarded and be replaced by others
denoting their chemical structure and their relation to such well-known
sterols as cholesterol. Long-accepted names will probably always be
retained. Thus it appears unlikely that the short name ergosterol will be
replaced by the more instructive but rather cumbersome 3ß-hydroxy-24amethyl-A
5 '
7 '
22 -cholestatriene or even the shorter 24a-methyl-7,22-bisdehydrocholesterol. The host of other sterols substituted by alkyl groups
at C-24 are best referred to as derivatives of cholesterol as was suggested by the author some time ago (17). The organic chemist knows
that the occasional, Babylonian confusion of names for natural products
will never be of long duration and will terminate once the structures
of the compounds have been ascertained. In contrast, no end appears
to be in sight to the exasperating confusion caused by the multiplicity
of names for biological species and the lack of agreement in their
application.
B. STRUCTURES
Until a few years ago the term sterols embraced only those steroids
that differ from cholesterol only in the number and position of double
bonds in the rings or the side chain, or the attachment to the side chain
of substituents such as alkyl groups at C-24. With the recognition of
the structural and biosynthetic connections between sterols and triterpenoids such "methylsterols" as lanosterol and agnosterol (VI and VII;
R = B) must also be included among the natural sterols. At present,
however, very little is known about the occurrence of methylsterols in
animal tissues or products other than wool grease (lanolin).
The sterols which are known or suspected to occur in animals may