78
2. Sterols
Saringosterol has two unusual features—a 24-vinyl (rather than the
customary ethylidene) group and a 24-hydroxy group. Only scymnol (15)
(see Section B,9) shares with saringosterol the 24-hydroxy function.
11.
DEMETHYLGORGOSTEROL
Although this unusual sterol, which was isolated by Schmitz and Pattabhiraman (1970) from the coelenterates Gorgonia flabellum or G. ventilina, is a
C 29 sterol, it is more conveniently discussed with the C 30 sterols, since it
shares with several of these compounds the characteristic cyclopropyl
group in the side chain.
E. C 30 Sterols
Four of these unusual C 30 sterols have been isolated in recent years, but a
fifth, demethylgorgosterol (see Section D,ll), while a C 29 compound, is
really a member of this group. Unlike the C 30 triterpenoids none of these
compounds possesses an additional carbon atom in the cyclopentanoperhydrophenanthrene portion of the molecule. All additional carbon atoms are
in the side chain and the characteristic feature of all but one of these compounds is the cyclopropane ring bridging carbon atoms 22 and 23. The
cyclopropyl-bearing compounds will be discussed first.
1. GORGOSTEROL
Bergmann et al. (1943) in the course of their examination of the sterols of
marine invertebrates studied the sterols of the gorgonian Plexaura flexuosa.
Quantitative saponification of the steryl acetate indicated an unusually high
molecular weight of 474 corresponding to a free sterol of composition
C30H50O to C31H54O. Further purification via the dibromoacetate led to a
substance, mp 180-185°, [a] D —45°, that was designated gorgosterol by
Bergmann et al. (1943). In a review article Bergmann (1962) wrote with
intuitive foresight, "Such exceptionally high melting points set these sterols
apart from other levorotatory A
5 -sterols and suggest the presence of a side
chain or other structural features not heretofore encountered."
Gupta (1967) studied the sterols of some coelenterates, among them the
zoanthid Palythoa tuberculosa. The physical constants of the sterol component were nearly identical with those reported by Bergmann et al. (1951)
for "palysterol" isolated from Palythoa mammilosa and then believed to be
homogeneous and isomeric with y-sitosterol. A direct comparison of Gupta's
Palythoa sterol and Bergmann's "palysterol" was not possible since no
sample of "palysterol" could be secured. A mass spectrum of Gupta's
Palythoa sterol showed this sterol to be a mixture of six components of
2. Sterols
Saringosterol has two unusual features—a 24-vinyl (rather than the
customary ethylidene) group and a 24-hydroxy group. Only scymnol (15)
(see Section B,9) shares with saringosterol the 24-hydroxy function.
11.
DEMETHYLGORGOSTEROL
Although this unusual sterol, which was isolated by Schmitz and Pattabhiraman (1970) from the coelenterates Gorgonia flabellum or G. ventilina, is a
C 29 sterol, it is more conveniently discussed with the C 30 sterols, since it
shares with several of these compounds the characteristic cyclopropyl
group in the side chain.
E. C 30 Sterols
Four of these unusual C 30 sterols have been isolated in recent years, but a
fifth, demethylgorgosterol (see Section D,ll), while a C 29 compound, is
really a member of this group. Unlike the C 30 triterpenoids none of these
compounds possesses an additional carbon atom in the cyclopentanoperhydrophenanthrene portion of the molecule. All additional carbon atoms are
in the side chain and the characteristic feature of all but one of these compounds is the cyclopropane ring bridging carbon atoms 22 and 23. The
cyclopropyl-bearing compounds will be discussed first.
1. GORGOSTEROL
Bergmann et al. (1943) in the course of their examination of the sterols of
marine invertebrates studied the sterols of the gorgonian Plexaura flexuosa.
Quantitative saponification of the steryl acetate indicated an unusually high
molecular weight of 474 corresponding to a free sterol of composition
C30H50O to C31H54O. Further purification via the dibromoacetate led to a
substance, mp 180-185°, [a] D —45°, that was designated gorgosterol by
Bergmann et al. (1943). In a review article Bergmann (1962) wrote with
intuitive foresight, "Such exceptionally high melting points set these sterols
apart from other levorotatory A
5 -sterols and suggest the presence of a side
chain or other structural features not heretofore encountered."
Gupta (1967) studied the sterols of some coelenterates, among them the
zoanthid Palythoa tuberculosa. The physical constants of the sterol component were nearly identical with those reported by Bergmann et al. (1951)
for "palysterol" isolated from Palythoa mammilosa and then believed to be
homogeneous and isomeric with y-sitosterol. A direct comparison of Gupta's
Palythoa sterol and Bergmann's "palysterol" was not possible since no
sample of "palysterol" could be secured. A mass spectrum of Gupta's
Palythoa sterol showed this sterol to be a mixture of six components of