120
WERNER BERGMANN
7. Group VII. Dimethyl- and Methylsterols
The biochemical conversion of a trimethylsterol such as lanosterol
(IX) to cholesterol (XIII) involves the loss of the methyl groups at
4,4 and 14. This elimination proceeds in all probability stepwise over
dimethyl- and monomethylsterols. As a rule such sterols appear to
have only a transitory existence. Nevertheless their presence in small
but demonstrable quantities in sterol mixtures is to be expected. In an
ingenious series of experimentations, Gautschi and Bloch (55) have
recently proved the occurrence of a dimethylsterol, X, in rats killed
soon after an injection of labeled acetate. This sterol and heretofore
been an important "missing link" in the sequence leading from lanosterol
(IX) to zymosterol (XI).
Monomethylsterols have also been found in sterol mixtures. 4aMethyl-A
7 -cholestenol (XII) was first obtained from rat feces (56). It
has recently been shown to be identical with a cactus sterol, lophenol
(57), C 28 H 48 0, m.p. 149-151°, [a] D +5°; acetate, m.p. 121°, [ a ] D +28°.
It is now to be expected that all sterols of the groups (I) to (V) with
the side chains A-M will also be found in nature as their mono-, di-,
and trimethyl derivatives. As yet only a few additional representatives
of this very large group of possible compounds have been found in
plant sterol mixtures. The best characterized of these is citrostadienol
or 4a-methyl-24-ethylidene-A
7 -cholestenol (58) (ring structure of XII,
and side chain I), C 3 oH 5 oO, m.p. 162-164°, [a] D +24°; acetate, m.p.
142-143°, [a] D +43°. It is obtainable from the oil of orange and grapefruit peel. The suggestion has been made that the long-known «i-sitosterol, m.p. 164-166°, [a] D —1.7°; acetate, m.p. 137°, [a] D +29°; differs
from citrostadienol only in the configuration around the 24,28-double
bond (59).
III. Sterols of Bacteria and Protozoa
Doree envisaged the possibility that sterols are not of primary
importance to all forms of life and that animals might be found "into
the composition of whose protoplasms it did not enter." Since then no
animal entirely devoid of sterols has been found, but there is good
evidence that sterols may not be necessary to* all forms of life. It was
first reported in 1889 (60) that no sterols could be detected in the
lipids of tubercle bacilli by means of the conventional color reactions.
Since then similar observations were made with diphtheria bacilli,
"Bacillus Calmette-Guerin
,, (Mycobacterium tuberculosis),
Escherichia
coli, and Mycobacterium lacticola. They were verified by the particularly
careful studies of von Behring (61) and of Anderson and his associates
WERNER BERGMANN
7. Group VII. Dimethyl- and Methylsterols
The biochemical conversion of a trimethylsterol such as lanosterol
(IX) to cholesterol (XIII) involves the loss of the methyl groups at
4,4 and 14. This elimination proceeds in all probability stepwise over
dimethyl- and monomethylsterols. As a rule such sterols appear to
have only a transitory existence. Nevertheless their presence in small
but demonstrable quantities in sterol mixtures is to be expected. In an
ingenious series of experimentations, Gautschi and Bloch (55) have
recently proved the occurrence of a dimethylsterol, X, in rats killed
soon after an injection of labeled acetate. This sterol and heretofore
been an important "missing link" in the sequence leading from lanosterol
(IX) to zymosterol (XI).
Monomethylsterols have also been found in sterol mixtures. 4aMethyl-A
7 -cholestenol (XII) was first obtained from rat feces (56). It
has recently been shown to be identical with a cactus sterol, lophenol
(57), C 28 H 48 0, m.p. 149-151°, [a] D +5°; acetate, m.p. 121°, [ a ] D +28°.
It is now to be expected that all sterols of the groups (I) to (V) with
the side chains A-M will also be found in nature as their mono-, di-,
and trimethyl derivatives. As yet only a few additional representatives
of this very large group of possible compounds have been found in
plant sterol mixtures. The best characterized of these is citrostadienol
or 4a-methyl-24-ethylidene-A
7 -cholestenol (58) (ring structure of XII,
and side chain I), C 3 oH 5 oO, m.p. 162-164°, [a] D +24°; acetate, m.p.
142-143°, [a] D +43°. It is obtainable from the oil of orange and grapefruit peel. The suggestion has been made that the long-known «i-sitosterol, m.p. 164-166°, [a] D —1.7°; acetate, m.p. 137°, [a] D +29°; differs
from citrostadienol only in the configuration around the 24,28-double
bond (59).
III. Sterols of Bacteria and Protozoa
Doree envisaged the possibility that sterols are not of primary
importance to all forms of life and that animals might be found "into
the composition of whose protoplasms it did not enter." Since then no
animal entirely devoid of sterols has been found, but there is good
evidence that sterols may not be necessary to* all forms of life. It was
first reported in 1889 (60) that no sterols could be detected in the
lipids of tubercle bacilli by means of the conventional color reactions.
Since then similar observations were made with diphtheria bacilli,
"Bacillus Calmette-Guerin
,, (Mycobacterium tuberculosis),
Escherichia
coli, and Mycobacterium lacticola. They were verified by the particularly
careful studies of von Behring (61) and of Anderson and his associates