3.2 Linear Sesterterpenoids with a 2-Furanone Moiety
Linear sesterterpenoids with a 2-furanone moiety also exist. The formation of the
2-furanone moiety should be similar to that of the furan ring moiety. Two possible
pathways are shown in Figs. 22 and 23.
Two linear sesterterpenoids with a 2-furanone moiety, 29 and 30, were isolated
from the Caribbean sponge Thorecta horridus (Fig. 24) [22]. In particular, 29
possesses potent inflammatory activity, inducing histamine release (in vitro), and
causes edema in rat paws (in vivo).
Compound 29 has also been reported from the Australian sponge Luffariella
geometrica, and designated as luffarin Q [23]. Luffarin R (31) was also isolated from
the same sponge (Fig. 25) [23]. Compound 31 possesses a γ-butyrolactone moiety in
addition to the 2-furanone moiety.
O
HO
OH
H +
oxidation
furan ring moiety
O
O
OH
aromatization
oxidation
O
O
O
O
2-furanone moiety
Fig. 22 Formation of the
2-furanone moiety
OH
O
OH
H +
oxidation
furan ring moiety
O
O
HO
aromatization
oxidation
O
O
O
O
2-furanone moiety
Fig. 23 An alternative
pathway for the formation of
the 2-furanone moiety
Sesterterpenoids
15