Organic Syntheses, Coll. Vol. 2, p.191 (1943); Vol. 17, p.45 (1937).
) From Cholesterol
.—One hundred grams (0.26 mole) of commercial cholesterol
is crystallized from 250 cc. of glacial acetic acid
, using 1 g. of Norite
if required, and the purified material (Note 1)
is transferred, conveniently without being dried, to a hydrogenation vessel
equipped with a thermometer
and a heating device (Note 2)
. Three hundred cubic centimeters of purified glacial acetic acid (Note 3)
and 0.5 g. of platinum oxide
are added, and the hydrogenation is conducted at 65–75° at a slight positive pressure. The total amount of hydrogen
usually is absorbed in two to four hours (Note 4)
. After the hydrogen
has been replaced by air the solution is filtered hot and the product is obtained by crystallization and concentration. The total yield of air-dried, partially acetylated dihydrocholesterol
, m.p. 130–135°
, is 85–90 g.
Unless a specially purified product (see below) is desired, the crude material is heated for three hours on the steam bath
with 400 cc. of alcohol
and a solution of 25 g. of sodium hydroxide
in 100 cc. of water. After cooling, the product is collected, washed, and crystallized from 500 cc. of alcohol
. The yield is 75–80 g.
per cent of the theoretical amount), and a well-dried sample (Note 5)
melts at 140–141°
) From Cholesteryl Acetate (Note 6)
.—Five grams of cholesteryl acetate (Note 7)
and 0.1 g. of platinum oxide
are suspended in 25 cc. of absolute ether
and 50 cc. of purified glacial acetic acid (Note 3)
, and the hydrogenation is conducted at room temperature at a slight positive pressure. The reaction is complete in ten to fifty minutes. The solution is filtered, using ether
to dissolve any crystallized material, and, after removing the solvent by distillation at reduced pressure, the residue is either saponified as above or purified in the following manner.
Purification by the Method of Anderson and Nabenhauer
—A solution of 20 g. of crude, partially or completely acetylated dihydrocholesterol
in 200 cc. of carbon tetrachloride
is placed in a separatory funnel
and treated with 100 cc. of acetic anhydride
. About 5 cc. of concentrated sulfuric acid
is added dropwise through the stem of the inverted funnel with cooling and shaking until there is no further increase in color. A blue or green color develops, the intensity depending on the amount of cholesterol
present in the sample. After fifteen to twenty minutes about 10 cc. of water is added, by drops and with cooling and gentle shaking until two distinct layers form. The carbon tetrachloride
solution (upper layer) is separated and washed free of acid with sodium chloride
or sodium carbonate
solution (pure water gives emulsions). After drying with sodium sulfate
, the solvent is removed by distillation at diminished pressure and the residue is saponified as above with alcoholic alkali and crystallized from alcohol. The purified dihydrocholesterol
weighs 12–14 g.
and melts, after thorough drying (Note 5)
, at 142–143°
. It gives a faint Liebermann-Burchard reaction (Note 8)
only after ten to fifteen minutes.
The dry weight of the crystallized material is 90–95 g.
Some samples may require recrystallization.
A suitable arrangement for heating the hydrogenation vessel is described in Org. Syn. Coll. Vol. I, 1941, 61
. An alternative arrangement is the following: a round-bottomed long-necked flask
is supported at the top by a two-piece clamp with a loosened checknut, connected below to an eccentric, and heated in motion by means of a stationary microburner
The catalyst sometimes loses its activity when about half of the theoretical amount of hydrogen
has been absorbed, probably because of the poisoning action of impurities not removed from the commercial cholesterol
. If this happens the addition of one or two 0.2-g. portions of catalyst usually suffices to bring the reaction practically to completion.
The sterol forms a hydrate from which the water is eliminated only after thorough drying, as in vacuum at 100°.
The acetyl derivative is more easily reduced than the free sterol.
This preparation is referenced from:
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