22
/. Isoprenoids
Ο
59
The authors (Fattorusso et al, 1971) speculate on the biogenetic origin of
these interesting C 21 compounds. They prefer the idea that nitenin and
dihydronitenin arose from degradation of a larger terpenoid over the possibility of synthesis by addition of a C-l unit, since the Italian workers now
isolated several C 25 (sester) terpenoids from the sponges, Ircinia oros (Cimino
et ai, 1972) and Lfasciculata (Cafieri et al, 1972).
Table 1.2 lists the marine diterpenoids and the related C 19 and C 2 i compounds.
TABLE 1.2
MARINE DITERPENOIDS
mp
Text no.
Name
(in degrees) [a] D °
Reference
49
Aplysin-20
146-147
-78.1
Matsudae/a/. (1967)
50
Crassin acetate
144-144.5
+70.7
Ciereszko et al. (1960)
51
Eunicin
154-155.5
-89.4
Weinheimer et al.
(1968a)
52
Jeunicin
139-141
+12.8
Weinheimer et al.
(1968b)
53
2,6,10,14-Tetramethyl—
S0rensen and
pentadecane (pristane)
Sorensen (1949)
55
2,6,10,14-tetramethyl-l—
Christensen and
pentadecene (zamene)
Sorensen (1951)
57
Nitenin
—
-45.4
Fattorusso et al. (1971)
59
Dihydronitenin
—
-25.2
Fattorusso et al. (1971)
C. Triterpenoids
All except two of the triterpenoid compounds that have so far been isolated
and characterized from marine sources are elaborated by members of a
single phylum of exclusively marine invertebrates, the echinoderms (Echinodermata). The phylum comprises about 5300 described species and includes
some of the most familiar representatives of sea life, e.g., sea stars (starfish)
and sea urchins. The phylum is characterized by radial symmetry, and some
of the animals are spectacularly beautiful in form and color.