C. Triterpenoids
27
the strong peak of which at m\e 99 corresponding to C e H n O was assigned to
fragment 64.
OAc
X> v ^
/
ν ~ t
Ij^^
mi.iOH
AcO^^^y^N^
Η
64
65
Strong chemical evidence for the nature and position of the lactone was
derived from lithium aluminum hydride reduction of 63a to a tetrol and its
conversion to a diol diacetate (65), the structure of which is in accord with
its spectral properties. Specifically, two new one-proton doublets centered at
3.86 and 4.30 ppm (/ = 12 Hz) are readily assigned to two nonequivalent
hydrogen atoms at C-18.
The diol diacetate 65 was further degraded by lead tetraacetate oxidation to
two ketones without loss of carbon : a 22-carbon compound 66 and a volatile
OAc
I
^CH 2
Aco'yr/
'i η
66
67
fragment (67) having eight carbon atoms. The spectral properties of compound 66 demonstrated conclusively that the side chain in the holothurinogenin 63 is attached to C-17 as is the tertiary hydroxyl.
The 7:8, 9:11 diene system was confirmed by several chemical transformations. Perhaps the most direct method was by oxidation of the acetate
of 63a with chromic oxide to a yellow trans ene-dione 68, A ma x 280 nm
(ε6390). This result is characteristic of tetracyclic triterpenoids possessing a
7:8, 9:11 diene system (Ourisson et α/., 1964).
Spectral comparison with other triterpenoid derivatives in the lanosterol
and agnosterol series established the typical 3ß-hydroxy-4,4- ( gem-dimethyl
system for 63a.
27
the strong peak of which at m\e 99 corresponding to C e H n O was assigned to
fragment 64.
OAc
X> v ^
/
ν ~ t
Ij^^
mi.iOH
AcO^^^y^N^
Η
64
65
Strong chemical evidence for the nature and position of the lactone was
derived from lithium aluminum hydride reduction of 63a to a tetrol and its
conversion to a diol diacetate (65), the structure of which is in accord with
its spectral properties. Specifically, two new one-proton doublets centered at
3.86 and 4.30 ppm (/ = 12 Hz) are readily assigned to two nonequivalent
hydrogen atoms at C-18.
The diol diacetate 65 was further degraded by lead tetraacetate oxidation to
two ketones without loss of carbon : a 22-carbon compound 66 and a volatile
OAc
I
^CH 2
Aco'yr/
'i η
66
67
fragment (67) having eight carbon atoms. The spectral properties of compound 66 demonstrated conclusively that the side chain in the holothurinogenin 63 is attached to C-17 as is the tertiary hydroxyl.
The 7:8, 9:11 diene system was confirmed by several chemical transformations. Perhaps the most direct method was by oxidation of the acetate
of 63a with chromic oxide to a yellow trans ene-dione 68, A ma x 280 nm
(ε6390). This result is characteristic of tetracyclic triterpenoids possessing a
7:8, 9:11 diene system (Ourisson et α/., 1964).
Spectral comparison with other triterpenoid derivatives in the lanosterol
and agnosterol series established the typical 3ß-hydroxy-4,4- ( gem-dimethyl
system for 63a.