118
WERNER BERGMANN
Cholestanol (dihydrocholesterol; ß-cholestanol) (IV, R = A), C 27
H 48 0, m.p. 142°, [a] D +24°, infrared spectrum (26); acetate, m.p. 111°,
[«]D +13.5°. It is a companion, 1-2%, of cholesterol in nearly all commercial preparations. In sterol mixtures from sponges it may occur in
quantities well in excess of 50%.
24ß-Methyl-A
22 -cholestenol
(neospongosterol) (IV, R = H), m.p.
150°, [ a ] D +10°; acetate, m.p. 126°, [a] D +8°. It is the only natural
sterol now known which is unsaturated in the side chain only (50). It
has been isolated from the spongosterol mixture of certain sponges.
The following saturated sterols have either been isolated from plant
sterol mixtures or obtained by catalytic hydrogenation of other natural
sterols. They are included because of their probable occurrence as minor
components in sterol mixtures from invertebrates.
24a-Methylcholestanol
(ergostanol) (IV, R = E), C 28 H 5 oO, m.p.
145°, [ a ] D +16°, infrared spectrum (26); acetate, m.p. 145°, [a] D +6°.
24ß-Meihylcholestanol
(campestanol) (IV, R = G), C 2 8H 5 oO, m.p.
147°, [a] D +31°; acetate, m.p. 144°, [ a ] D +18°.
24a-Ethylcholestanol (stigmastanol; ß-sitostanol; dihydro-ß-sitosterol)
(IV, R = J), C 29 H 52 0, m.p. 138°, [ a ] D +25°; acetate, m.p. 132°, [a] D
+25°.
24ß-Ethylcholestanol (γ-sitostanol; dihydro-y-sitosterol; poriferastanol)
(IV, R = L), Co 9 H 5 oO, m.p. 144°, [a] D +19°; acetate, m.p. 144°, [a] D
+10.
5. Group V (Structure V): Δ
8(9) -Sterols with Specific Rotations of -\-30°
to +50°
As yet only three natural representatives of this group have become
known, and the structure of only one of them has been established with
certainty. All of them are components of the mixtures of minor yeast
sterols left after the removal of ergosterol. The Δ
8(9) -sterols, which also
have been called "8"-sterols resemble the A
7 -sterols in many of their
reactions, but they differ from them in their pronounced dextrorotation.
The molecular rotation differences between the sterols and their acetates
and benzoates are —46.5 and +11.5, respectively (31). Renewed interest in these sterols has grown out of the realization that sterols of
type V may constitute intermediate steps in the biosynthesis of other
sterols. It is probable that a thorough search will reveal their presence in
many sterol mixtures.
Zymosterol (A
8(9) '
24 -cholestadienol) (V, R = B), C 27 H 44 0, m.p. 110°,
[a] D +49°; acetate, m.p. 108°, [a] D +35°. This sterol, first discovered
as one of the most common components of the minor yeast sterol mixtures has assumed considerable importance in the discussions and ex-
WERNER BERGMANN
Cholestanol (dihydrocholesterol; ß-cholestanol) (IV, R = A), C 27
H 48 0, m.p. 142°, [a] D +24°, infrared spectrum (26); acetate, m.p. 111°,
[«]D +13.5°. It is a companion, 1-2%, of cholesterol in nearly all commercial preparations. In sterol mixtures from sponges it may occur in
quantities well in excess of 50%.
24ß-Methyl-A
22 -cholestenol
(neospongosterol) (IV, R = H), m.p.
150°, [ a ] D +10°; acetate, m.p. 126°, [a] D +8°. It is the only natural
sterol now known which is unsaturated in the side chain only (50). It
has been isolated from the spongosterol mixture of certain sponges.
The following saturated sterols have either been isolated from plant
sterol mixtures or obtained by catalytic hydrogenation of other natural
sterols. They are included because of their probable occurrence as minor
components in sterol mixtures from invertebrates.
24a-Methylcholestanol
(ergostanol) (IV, R = E), C 28 H 5 oO, m.p.
145°, [ a ] D +16°, infrared spectrum (26); acetate, m.p. 145°, [a] D +6°.
24ß-Meihylcholestanol
(campestanol) (IV, R = G), C 2 8H 5 oO, m.p.
147°, [a] D +31°; acetate, m.p. 144°, [ a ] D +18°.
24a-Ethylcholestanol (stigmastanol; ß-sitostanol; dihydro-ß-sitosterol)
(IV, R = J), C 29 H 52 0, m.p. 138°, [ a ] D +25°; acetate, m.p. 132°, [a] D
+25°.
24ß-Ethylcholestanol (γ-sitostanol; dihydro-y-sitosterol; poriferastanol)
(IV, R = L), Co 9 H 5 oO, m.p. 144°, [a] D +19°; acetate, m.p. 144°, [a] D
+10.
5. Group V (Structure V): Δ
8(9) -Sterols with Specific Rotations of -\-30°
to +50°
As yet only three natural representatives of this group have become
known, and the structure of only one of them has been established with
certainty. All of them are components of the mixtures of minor yeast
sterols left after the removal of ergosterol. The Δ
8(9) -sterols, which also
have been called "8"-sterols resemble the A
7 -sterols in many of their
reactions, but they differ from them in their pronounced dextrorotation.
The molecular rotation differences between the sterols and their acetates
and benzoates are —46.5 and +11.5, respectively (31). Renewed interest in these sterols has grown out of the realization that sterols of
type V may constitute intermediate steps in the biosynthesis of other
sterols. It is probable that a thorough search will reveal their presence in
many sterol mixtures.
Zymosterol (A
8(9) '
24 -cholestadienol) (V, R = B), C 27 H 44 0, m.p. 110°,
[a] D +49°; acetate, m.p. 108°, [a] D +35°. This sterol, first discovered
as one of the most common components of the minor yeast sterol mixtures has assumed considerable importance in the discussions and ex-