80
2. Sterols
37
sterol has an alkyl branch at C-22. The complete structure, including absolute
configuration, was secured by X-ray diffraction determination of 3-bromogorgostene obtained from gorgosterol by treatment with aluminum bromide
(Ling et al, 1970) and was shown to be (227?, 23i?, 247?)-23,24-dimethylcholest-5-en-3ß-ol (36). While alkylation at C-24 is common, the C-23
methyl group and the three-membered ring between carbon atoms 22 and 23
are without precedent.
30
/\ 29 24
Γ
23
36
2. ACANTHASTEROL
Gupta (1967) in his examination of echinoderm sterols showed that
the sterol mixture of the sea star Acanthaster planci consisted of six compounds. Furthermore one of the sterols had an unusually long glc retention
time and the spectral characteristics of this sterol were strongly reminiscent
of gorgosterol (Gupta and Scheuer, 1968). Gupta and Scheuer (1968) were
aware of the Δ
7 structural feature of sea star sterols and suggested therefore
that this new sterol, acanthasterol, was the A
7 -analog of gorgosterol. Because
of lack of material they were unable to prove it. Sheikh et al. (1971a) reisolated
the compound from the same organism and showed by direct comparison of
dihydroacanthasterol with dihydrogorgosterol that Gupta and Scheuer's
(1968) assumption was correct and that acanthasterol had structure 37.
Sheikh et al. (1971a) erroneously coined for this sterol a new trivial name
(acansterol), which they (Sheikh et al., 1971b) subsequently withdrew.
2. Sterols
37
sterol has an alkyl branch at C-22. The complete structure, including absolute
configuration, was secured by X-ray diffraction determination of 3-bromogorgostene obtained from gorgosterol by treatment with aluminum bromide
(Ling et al, 1970) and was shown to be (227?, 23i?, 247?)-23,24-dimethylcholest-5-en-3ß-ol (36). While alkylation at C-24 is common, the C-23
methyl group and the three-membered ring between carbon atoms 22 and 23
are without precedent.
30
/\ 29 24
Γ
23
36
2. ACANTHASTEROL
Gupta (1967) in his examination of echinoderm sterols showed that
the sterol mixture of the sea star Acanthaster planci consisted of six compounds. Furthermore one of the sterols had an unusually long glc retention
time and the spectral characteristics of this sterol were strongly reminiscent
of gorgosterol (Gupta and Scheuer, 1968). Gupta and Scheuer (1968) were
aware of the Δ
7 structural feature of sea star sterols and suggested therefore
that this new sterol, acanthasterol, was the A
7 -analog of gorgosterol. Because
of lack of material they were unable to prove it. Sheikh et al. (1971a) reisolated
the compound from the same organism and showed by direct comparison of
dihydroacanthasterol with dihydrogorgosterol that Gupta and Scheuer's
(1968) assumption was correct and that acanthasterol had structure 37.
Sheikh et al. (1971a) erroneously coined for this sterol a new trivial name
(acansterol), which they (Sheikh et al., 1971b) subsequently withdrew.