72
2. Sterols
7. 24-METHYLCHOLESTA-7,24(28)-DIEN-3£-OL [7,24(28)-ERGOSTADIEN-3jS-OL,
EPISTEROL]
The A
7 -analog of 24-methyleneeholesterol (22) has so far been reported
only once from a marine organism. Fagerlund and Idler (1959) isolated
24-methylcholesta-7,24(28)-dien-3jS-ol (23) from asteroid Pisaster ochraceus
by chromatography of the steryl p-phenylazobenzoates and secured its
structure. This sterol was also shown by Knights (1967) to be present in
oat seed.
23
D. C 29 Sterols
With one additional carbon atom in the side chain several new structural
possibilities can arise. Not all possible structures have been found, but
members of the C 29 group contain several novel and interesting features.
The C-24 ethyl group that is present in all but one of the C 29 sterols may be
unsaturated as an ethylidene or as a vinyl group. If it is an ethylidene group,
geometrical isomerism at the 24,28-double bond may arise and one such
pair (fucosterol, avenasterol) has come to light. The single example to date
of a 24-vinyl group has the additional feature of a 24-hydroxy group, thus
making it (saringosterol) one of the few diols among marine sterols. Another
fascinating member of the C 29 group is a 23-demethylgorgosterol with the
side-chain cyclopropane group.
1. 24a-ETHYLCHOLEST-5-EN-3ß-OL (β-SITOSTEROL)
jS-Sitosterol (24) is a widely distributed plant sterol, but it has long been
recognized that few of the sterol samples that have been so designated over the
years are pure 24a-ethylcholest-5-en-3/3-ol (Brooks, 1970). Judging from a few
carefully documented recent reports, j8-sitosterol does not appear to be
widely found in marine organisms. Its most substantial occurrence (40% of
the mixture) has been reported by Ikekawa et al. (1968) from the green alga
Chaetomorpha crassa. Idler et al. (1968) have reported small amounts in a
2. Sterols
7. 24-METHYLCHOLESTA-7,24(28)-DIEN-3£-OL [7,24(28)-ERGOSTADIEN-3jS-OL,
EPISTEROL]
The A
7 -analog of 24-methyleneeholesterol (22) has so far been reported
only once from a marine organism. Fagerlund and Idler (1959) isolated
24-methylcholesta-7,24(28)-dien-3jS-ol (23) from asteroid Pisaster ochraceus
by chromatography of the steryl p-phenylazobenzoates and secured its
structure. This sterol was also shown by Knights (1967) to be present in
oat seed.
23
D. C 29 Sterols
With one additional carbon atom in the side chain several new structural
possibilities can arise. Not all possible structures have been found, but
members of the C 29 group contain several novel and interesting features.
The C-24 ethyl group that is present in all but one of the C 29 sterols may be
unsaturated as an ethylidene or as a vinyl group. If it is an ethylidene group,
geometrical isomerism at the 24,28-double bond may arise and one such
pair (fucosterol, avenasterol) has come to light. The single example to date
of a 24-vinyl group has the additional feature of a 24-hydroxy group, thus
making it (saringosterol) one of the few diols among marine sterols. Another
fascinating member of the C 29 group is a 23-demethylgorgosterol with the
side-chain cyclopropane group.
1. 24a-ETHYLCHOLEST-5-EN-3ß-OL (β-SITOSTEROL)
jS-Sitosterol (24) is a widely distributed plant sterol, but it has long been
recognized that few of the sterol samples that have been so designated over the
years are pure 24a-ethylcholest-5-en-3/3-ol (Brooks, 1970). Judging from a few
carefully documented recent reports, j8-sitosterol does not appear to be
widely found in marine organisms. Its most substantial occurrence (40% of
the mixture) has been reported by Ikekawa et al. (1968) from the green alga
Chaetomorpha crassa. Idler et al. (1968) have reported small amounts in a