30
/. Isoprenoids
spectral data showed praslinogenin (74) to be a hydroxylated ternaygenin
(73c). That praslinogenin (74) was indeed the 17-hydroxy compound could be
demonstrated by comparing the chemical shift of one of the terminal methyl
groups—it moves downfield from 1.00 to 1.15 ppm when one goes from
ternaygenin (73c) to praslinogenin (74). The same value (1.15 ppm) is
observed for a terminal methyl group in other 17a-hydroxy compounds,
e.g., griseogenin (69). Again, it is likely that praslinogenin (74) is an artifact
produced during glycoside hydrolysis.
Habermehl and Volkwein (1968) examined several species of Mediterranean
sea cucumbers and succeeded in isolating 22,25-oxidoholothurinogenin
(63a) as well as its 17-deoxy analog (63b) from Holothuria tubulosa. Paper
chromatography of the sugars indicated the presence of only an aldopentose
and the absence of sulfuric acid.
From another Mediterranean species, H. polii, Habermehl and Volkwein
(1970) were able to separate and identify by spectral comparison six aglycones
after acid hydrolysis. In addition to the known compounds 22-25-oxidoholothurinogenin (63a) and its 17-deoxy analog (63b), griseogenin (69), praslinogenin (74), and its deoxy analog ternaygenin (73c) the German workers
demonstrated the presence of the hypothetical parent compound of the
ιπιιιΟΗ
75
group, holothurinogenin (75). Interestingly, the aglycones of H. polii include
the two 25-methoxy compounds (73c, 74) without the corresponding 25hydroxy "precursors" in spite of the fact that aqueous hydrochloric acid is
the hydrolytic agent in an operation that is separate from the original aqueous
methanolic extraction. This would indicate that 25-methoxy compounds need
not be artifacts. Habermehl and Volkwein (1970) assign ^-configuration
(i.e., trans to the 17a-hydroxy group) to the C-21 methyl group, since this
methyl group exhibits the same chemical shift in the 22,25-oxido compound
(63a) and in the 25-methoxy compound (74).
Habermehl and Volkwein (1971) examined a third Mediterranean sea
cucumber, Holothuria forskâli, and isolated from the Cuvierian organs three
known genins—22,25-oxidoholothurinogenin (63a), 17-deoxy-22,25-oxido-
/. Isoprenoids
spectral data showed praslinogenin (74) to be a hydroxylated ternaygenin
(73c). That praslinogenin (74) was indeed the 17-hydroxy compound could be
demonstrated by comparing the chemical shift of one of the terminal methyl
groups—it moves downfield from 1.00 to 1.15 ppm when one goes from
ternaygenin (73c) to praslinogenin (74). The same value (1.15 ppm) is
observed for a terminal methyl group in other 17a-hydroxy compounds,
e.g., griseogenin (69). Again, it is likely that praslinogenin (74) is an artifact
produced during glycoside hydrolysis.
Habermehl and Volkwein (1968) examined several species of Mediterranean
sea cucumbers and succeeded in isolating 22,25-oxidoholothurinogenin
(63a) as well as its 17-deoxy analog (63b) from Holothuria tubulosa. Paper
chromatography of the sugars indicated the presence of only an aldopentose
and the absence of sulfuric acid.
From another Mediterranean species, H. polii, Habermehl and Volkwein
(1970) were able to separate and identify by spectral comparison six aglycones
after acid hydrolysis. In addition to the known compounds 22-25-oxidoholothurinogenin (63a) and its 17-deoxy analog (63b), griseogenin (69), praslinogenin (74), and its deoxy analog ternaygenin (73c) the German workers
demonstrated the presence of the hypothetical parent compound of the
ιπιιιΟΗ
75
group, holothurinogenin (75). Interestingly, the aglycones of H. polii include
the two 25-methoxy compounds (73c, 74) without the corresponding 25hydroxy "precursors" in spite of the fact that aqueous hydrochloric acid is
the hydrolytic agent in an operation that is separate from the original aqueous
methanolic extraction. This would indicate that 25-methoxy compounds need
not be artifacts. Habermehl and Volkwein (1970) assign ^-configuration
(i.e., trans to the 17a-hydroxy group) to the C-21 methyl group, since this
methyl group exhibits the same chemical shift in the 22,25-oxido compound
(63a) and in the 25-methoxy compound (74).
Habermehl and Volkwein (1971) examined a third Mediterranean sea
cucumber, Holothuria forskâli, and isolated from the Cuvierian organs three
known genins—22,25-oxidoholothurinogenin (63a), 17-deoxy-22,25-oxido-