114
WERNER BERGMANN
versely, sterols suspected to be A
5 -unsaturated but with molecular rotation differences at variance with such values must be regarded as lacking uniformity or belonging to another group.
Cholesterol (II, R = A), C 27 H 46 0, m.p. 149.5-150°, [a] D -39.5°, infrared spectrum (26); acetate, m.p. 114-115°, [a] D —47.5°. It is the best
known and most readily available of all sterols. It is the typical sterol
of the vertebrates and has also been found in many invertebrates including protozoa and sponges (Sections III and IV). More recently it
has been isolated in significant quantities from a number of red algae
(32). This significant discovery has removed the last reason for the
artificial division of sterols into zoosterols, phytosterols, and mycosterols
which had so long been in use.
24-Dehydrocholesterol
(desmosterol)
(II, R = B), C 27 H 4 40, m.p.
117° (33), 120-121° (34); A max 2.96, 7.28, 12.51 ^ in KBr; [a] D -40°;
acetate, m.p. 92-93° (34), 101° (33), [a] D —41°. It is believed to represent one of the final steps in the biosynthesis of cholesterol. It has been
isolated in small amounts from chicken embryos (35) and in larger
quantities from barnacle sterols (33). The structure has been established
by degradation and synthesis (33, 34).
22-Dehydrocholesterol (II, R = C), C 27 H 44 0, m.p. 135°, [a] D —57°,
A max 2.97, 7.29, 7.34, 10.29, and 12.51 μ in KBr; acetate, m.p. 126°, [a] D
—63°. This sterol which as yet has become known only as synthetic
material (36) carries a side chain analogous in its unsaturation to those
found in many natural, 24-alkyl-substituted sterols (F, H, K, and M).
It has long been suspected to occur in some of the more complex sterol
mixtures. Its physical properties are so similar to those of ß-sitosterol
and of many poorly defined sterol mixtures that it may easily be missed.
24-Methylenecholesterol (chalinasterol) (II, R = D), C 28 H 46 0, m.p.
142° (37), 145-146° (38); [a] D -35° (37), -42° (38), infrared spectrum (38); acetate, m.p. 135-136°, [a] D —42 to —47°. It appears to be
quite widely distributed among many invertebrates such as sea anemones, sponges, and bivalves. Before its structure had first been established by Idler (37) it had been described under a variety of names
which will be discussed under mollusk sterols. The sterol has been
synthesized (38, 39).
24a-Methyhholesterol
(22,23-dihydrobrassicasterol)
(II, R = E),
C 28 H 4S 0, m.p. 158°, [a] D —46°; acetate, m.p. 145°, [a] D —46°. As yet
only obtained by selective hydrogenation of brassicasterol (II, R = F)
(40), this sterol may be assumed to occur in some of the unresolved
sterol mixtures from bivalves.
24ß-Methylcholesterol
(campesterol) (41) (II, R = G), C 28 H 48 0,
m.p. 158°, [a] D —33°; acetate, m.p. 138°, [a] D —35°. Although this
WERNER BERGMANN
versely, sterols suspected to be A
5 -unsaturated but with molecular rotation differences at variance with such values must be regarded as lacking uniformity or belonging to another group.
Cholesterol (II, R = A), C 27 H 46 0, m.p. 149.5-150°, [a] D -39.5°, infrared spectrum (26); acetate, m.p. 114-115°, [a] D —47.5°. It is the best
known and most readily available of all sterols. It is the typical sterol
of the vertebrates and has also been found in many invertebrates including protozoa and sponges (Sections III and IV). More recently it
has been isolated in significant quantities from a number of red algae
(32). This significant discovery has removed the last reason for the
artificial division of sterols into zoosterols, phytosterols, and mycosterols
which had so long been in use.
24-Dehydrocholesterol
(desmosterol)
(II, R = B), C 27 H 4 40, m.p.
117° (33), 120-121° (34); A max 2.96, 7.28, 12.51 ^ in KBr; [a] D -40°;
acetate, m.p. 92-93° (34), 101° (33), [a] D —41°. It is believed to represent one of the final steps in the biosynthesis of cholesterol. It has been
isolated in small amounts from chicken embryos (35) and in larger
quantities from barnacle sterols (33). The structure has been established
by degradation and synthesis (33, 34).
22-Dehydrocholesterol (II, R = C), C 27 H 44 0, m.p. 135°, [a] D —57°,
A max 2.97, 7.29, 7.34, 10.29, and 12.51 μ in KBr; acetate, m.p. 126°, [a] D
—63°. This sterol which as yet has become known only as synthetic
material (36) carries a side chain analogous in its unsaturation to those
found in many natural, 24-alkyl-substituted sterols (F, H, K, and M).
It has long been suspected to occur in some of the more complex sterol
mixtures. Its physical properties are so similar to those of ß-sitosterol
and of many poorly defined sterol mixtures that it may easily be missed.
24-Methylenecholesterol (chalinasterol) (II, R = D), C 28 H 46 0, m.p.
142° (37), 145-146° (38); [a] D -35° (37), -42° (38), infrared spectrum (38); acetate, m.p. 135-136°, [a] D —42 to —47°. It appears to be
quite widely distributed among many invertebrates such as sea anemones, sponges, and bivalves. Before its structure had first been established by Idler (37) it had been described under a variety of names
which will be discussed under mollusk sterols. The sterol has been
synthesized (38, 39).
24a-Methyhholesterol
(22,23-dihydrobrassicasterol)
(II, R = E),
C 28 H 4S 0, m.p. 158°, [a] D —46°; acetate, m.p. 145°, [a] D —46°. As yet
only obtained by selective hydrogenation of brassicasterol (II, R = F)
(40), this sterol may be assumed to occur in some of the unresolved
sterol mixtures from bivalves.
24ß-Methylcholesterol
(campesterol) (41) (II, R = G), C 28 H 48 0,
m.p. 158°, [a] D —33°; acetate, m.p. 138°, [a] D —35°. Although this