66
2. Sterols
8. MARTHASTERONE AND DIHYDROMARTHASTERONE
A C 27 steroid of unusual structure and unusual origin has recently been
characterized. As mentioned in Chapter 1, two classes of the echinoderms,
the sea cucumbers (holothurians) and the sea stars (asteroids), elaborate
saponins, presumably as defensive agents. The sea cucumbers with their
spectacular defense mechanism received early attention and a number of the
active compounds, the holothurins, have been well characterized as a group
of unique triterpenoid glycosides. The asterosaponins, on the other hand,
have been studied only recently. It had been tacitly assumed that, in analogy
with the holothurinogenins, the aglycones of the asterosaponins are triterpenoids. Two aglycones from the sea star Marthasterias glacialis have now
been characterized as steroids (Turner et al, 1971). Mackie and Turner
(1970) earlier described the isolation of the glycoside and determined the
probable sequence D-fucose-D-quinovose-D-quinovose-D-glucose-aglycone ;
the sulfate residue was presumably attached directly to the steroid nucleus.
Hydrochloric acid hydrolysis of the glycoside led to the aglycone, which was
resolvable into three components by glc. The two major constituents were
separated by tic—the uv active substance, marthasterone was assigned
structure 10a and was readily convertible into the second major component,
dihydromarthasterone (10b) by palladium-on-charcoal hydrogénation. The
structures were secured by a combination of spectral and chemical techniques.
Ο
OH
10
a: R = — CH=CMe 2
b: R = —CH 2 —CHMe 2
9.
SCYMNOL
A group of compounds known as the bile alcohols are a notable exception
to the generalization that highly polar sterols are being overlooked unless
—as was the case with the ecdysones—the isolation is monitored by bioassay.
At least one of these compounds, scymnol, was first described over seventy
years ago (Hammarsten, 1898) as a constituent of the bile of an Arctic shark,
Scymnus borealis. The so-called bile salts (Haslewood, 1967) are characteristic
2. Sterols
8. MARTHASTERONE AND DIHYDROMARTHASTERONE
A C 27 steroid of unusual structure and unusual origin has recently been
characterized. As mentioned in Chapter 1, two classes of the echinoderms,
the sea cucumbers (holothurians) and the sea stars (asteroids), elaborate
saponins, presumably as defensive agents. The sea cucumbers with their
spectacular defense mechanism received early attention and a number of the
active compounds, the holothurins, have been well characterized as a group
of unique triterpenoid glycosides. The asterosaponins, on the other hand,
have been studied only recently. It had been tacitly assumed that, in analogy
with the holothurinogenins, the aglycones of the asterosaponins are triterpenoids. Two aglycones from the sea star Marthasterias glacialis have now
been characterized as steroids (Turner et al, 1971). Mackie and Turner
(1970) earlier described the isolation of the glycoside and determined the
probable sequence D-fucose-D-quinovose-D-quinovose-D-glucose-aglycone ;
the sulfate residue was presumably attached directly to the steroid nucleus.
Hydrochloric acid hydrolysis of the glycoside led to the aglycone, which was
resolvable into three components by glc. The two major constituents were
separated by tic—the uv active substance, marthasterone was assigned
structure 10a and was readily convertible into the second major component,
dihydromarthasterone (10b) by palladium-on-charcoal hydrogénation. The
structures were secured by a combination of spectral and chemical techniques.
Ο
OH
10
a: R = — CH=CMe 2
b: R = —CH 2 —CHMe 2
9.
SCYMNOL
A group of compounds known as the bile alcohols are a notable exception
to the generalization that highly polar sterols are being overlooked unless
—as was the case with the ecdysones—the isolation is monitored by bioassay.
At least one of these compounds, scymnol, was first described over seventy
years ago (Hammarsten, 1898) as a constituent of the bile of an Arctic shark,
Scymnus borealis. The so-called bile salts (Haslewood, 1967) are characteristic