68
2. Sterols
Partial synthesis from a cholic acid derivative further proved that scymnol
was indeed 3a,7a,12a,24|,26,27-hexahydroxycoprostane (15).
OH
^^^^A^^CH 2 OH
?
H
Τ
CH 2 OH
Η
15
An interesting point in connection with the chemistry of scymnol (15)
is the observation that a bile alcohol, cyprinol, isolated from the (fresh
water) carp Cyprinus carpio is a pentahydroxycholestane of structure 16
(Hoshita et al, 1963; Anderson et al, 1964; Cross, 1964).
.
/\
/\
CH 2 OH
OH
γ ^<
1
I
CH 2 OH
H
16
C. C 28 Sterols
All C 28 marine sterols that have so far been characterized bear the additional
carbon atom at C-24. This new center of chirality gives rise to two series of
compounds epimeric with respect to C-24 in all cases where C-24 is a tetrahedral carbon. Not all possible combinations of structural features commonly
identified with marine sterols (unsaturation at C-5 or C-7 combined with
unsaturation at C-22 or C-24) have been reported and the configuration of the
C-24 methyl group has not been ascertained in all cases. Up to the present
it appears that seven C 28 marine sterols have been well characterized.
1. 24a-METHYLCHOLEST-5-EN-3j8-OL (CAMPESTEROL)
Campesterol (17) apparently has not been isolated as the major sterol
component of a marine organism. It is an authentic constituent of the sterols
of rape (Fernholz and Ruigh, 1941) and other terrestrial seed oils and has
been reported as a possible minor sterol constituent of the green alga Chaetomorpha crassa (Ikekawa et al, 1968) and of the coelenterate Zoanthus con-
2. Sterols
Partial synthesis from a cholic acid derivative further proved that scymnol
was indeed 3a,7a,12a,24|,26,27-hexahydroxycoprostane (15).
OH
^^^^A^^CH 2 OH
?
H
Τ
CH 2 OH
Η
15
An interesting point in connection with the chemistry of scymnol (15)
is the observation that a bile alcohol, cyprinol, isolated from the (fresh
water) carp Cyprinus carpio is a pentahydroxycholestane of structure 16
(Hoshita et al, 1963; Anderson et al, 1964; Cross, 1964).
.
/\
/\
CH 2 OH
OH
γ ^<
1
I
CH 2 OH
H
16
C. C 28 Sterols
All C 28 marine sterols that have so far been characterized bear the additional
carbon atom at C-24. This new center of chirality gives rise to two series of
compounds epimeric with respect to C-24 in all cases where C-24 is a tetrahedral carbon. Not all possible combinations of structural features commonly
identified with marine sterols (unsaturation at C-5 or C-7 combined with
unsaturation at C-22 or C-24) have been reported and the configuration of the
C-24 methyl group has not been ascertained in all cases. Up to the present
it appears that seven C 28 marine sterols have been well characterized.
1. 24a-METHYLCHOLEST-5-EN-3j8-OL (CAMPESTEROL)
Campesterol (17) apparently has not been isolated as the major sterol
component of a marine organism. It is an authentic constituent of the sterols
of rape (Fernholz and Ruigh, 1941) and other terrestrial seed oils and has
been reported as a possible minor sterol constituent of the green alga Chaetomorpha crassa (Ikekawa et al, 1968) and of the coelenterate Zoanthus con-