60
2. Sterols
There are a number of early reports (e.g., Bergmann et al, 1945) on the
isolation of marine sterols that are saturated in the nucleus, such as cholestanol and 24a-methylcholest-22-en-3ß-ol (22,23-dehydrocampestanol). The
latter is referred to as spongesterol, mp 150°, [a] D +10°, in the current
literature (Brooks, 1970) and is presumably what Bergmann et al. (1945)
called neospongosterol, when they isolated from the sponge Suberites
compacta, a sterol that appeared to be identical with Henze's (1904, 1908)
first marine sterol, spongosterol, but which they could separate into cholestanol and new sterol, mp 153°, [α] Ό +10°. A modern reinvestigation (Erdman*
and Thomson, 1972) of the sterols of two sponges Cliona celata and Hymeniacidon perleve has finally confirmed the presence of cholestanol and other
sterols possessing a saturated sterol nucleus. In the sponge Hymeniacidon
perleve cholestanol is in fact the predominant sterol.
Pertinent data for the sterols are collected in Table 2.1 at the end of this
chapter.
A. C 26 Sterol
An unprecedented sterol with a C-7 side chain,
22-trans-2A-norcholesta5,22-diene-3ß-ol (1) was isolated by Idler et al. (1970) from the scallop (a
1
pelecypod mollusk, or bivalve) Placopecten magellanicus, where it occurs
as part of a mixture of at least ten components. It was isolated by glc either
as the trimethylsilyl or the methyl ether, and its structure was determined by
spectral methods. The same norcholestadiene was detected by glc in other
pelecypods and on the basis of retention-time comparison it is likely to
occur in crustaceans and red algae as well.
Fry berg and co-workers (1971a, 1972) have synthesized the C 26 sterol via
a Wittig reaction on the C-22 aldehyde. The requisite aldehyde was prepared
from stigmasterol (21) by a new degradation sequence that involved selective
bromination of the 5,6-double bond with iodobenzene dibromide (Fryberg
et al., 1971b). Synthetic and natural sterols were shown to be identical.
* I am indebted to Dr. Erdman for a preprint of this paper.
2. Sterols
There are a number of early reports (e.g., Bergmann et al, 1945) on the
isolation of marine sterols that are saturated in the nucleus, such as cholestanol and 24a-methylcholest-22-en-3ß-ol (22,23-dehydrocampestanol). The
latter is referred to as spongesterol, mp 150°, [a] D +10°, in the current
literature (Brooks, 1970) and is presumably what Bergmann et al. (1945)
called neospongosterol, when they isolated from the sponge Suberites
compacta, a sterol that appeared to be identical with Henze's (1904, 1908)
first marine sterol, spongosterol, but which they could separate into cholestanol and new sterol, mp 153°, [α] Ό +10°. A modern reinvestigation (Erdman*
and Thomson, 1972) of the sterols of two sponges Cliona celata and Hymeniacidon perleve has finally confirmed the presence of cholestanol and other
sterols possessing a saturated sterol nucleus. In the sponge Hymeniacidon
perleve cholestanol is in fact the predominant sterol.
Pertinent data for the sterols are collected in Table 2.1 at the end of this
chapter.
A. C 26 Sterol
An unprecedented sterol with a C-7 side chain,
22-trans-2A-norcholesta5,22-diene-3ß-ol (1) was isolated by Idler et al. (1970) from the scallop (a
1
pelecypod mollusk, or bivalve) Placopecten magellanicus, where it occurs
as part of a mixture of at least ten components. It was isolated by glc either
as the trimethylsilyl or the methyl ether, and its structure was determined by
spectral methods. The same norcholestadiene was detected by glc in other
pelecypods and on the basis of retention-time comparison it is likely to
occur in crustaceans and red algae as well.
Fry berg and co-workers (1971a, 1972) have synthesized the C 26 sterol via
a Wittig reaction on the C-22 aldehyde. The requisite aldehyde was prepared
from stigmasterol (21) by a new degradation sequence that involved selective
bromination of the 5,6-double bond with iodobenzene dibromide (Fryberg
et al., 1971b). Synthetic and natural sterols were shown to be identical.
* I am indebted to Dr. Erdman for a preprint of this paper.