LPS-activated RAW264.7 macrophages. During the proposed cyclization reaction
for the formation of the 5/6/5/6/5-membered ring system starting from
geranylfarnesyl diphosphate (8), several complex rearrangements could occur
(Fig. 94).
8.1.2 5/7/3/6/5-Membered Ring System
Asperterpenoid A (131), with a 5/7/3/6/5-membered ring system, has been isolated
from a mangrove endophytic fungus, Aspergillus sp. 16-5c (Fig. 95) [118]. Compound 131 is a strong inhibitor of Mycobacterium tuberculosis protein tyrosine
phosphatase B. Its formation from geranylfarnesyl diphosphate (8) is illustrated in
Fig. 95.
OPP
8
H H
H
O
HO
OH
131
Fig. 95 Structure of asperterpenoid A (131), and possible cyclization reaction for the formation of
the 5/7/3/6/5-membered ring system of 131
52
T. Mitsuhashi and I. Abe