D. C 29 Sterols
75
30
28
6. 24/^ETHYLCHOLESTA-7,22-DIEN-3£-OL (CHONDRILLASTEROL)
The A
7 -analog of poriferasterol (28) is chondrillasterol (29) and structural
definition of this sterol parallels that of its A
5 -isomer. Bergmann and McTigue
(1948) isolated the sterol from the sponge Chondrilla nucula and proposed its
structure on the basis of degradations and comparisons that were feasible
at that time. Shortly thereafter Bergmann and Feeney (1950) isolated the
same sterol from the green alga Scenedesmus obliquus D 3 . Again, recent work
on this sterol is lacking.
29
7. 24-ETHYLCHOLESTA-5,22(28)-DIEN-3£-OL (FUCOSTEROL)
Fucosterol (30) is generally considered to be the principal sterol of brown
algae and represents one of the fortuitous exceptions to the general remarks