10.4 6/6/7/5- and 6/11/5-Membered Ring Systems
A sesterterpene synthase, identified from the genetic data of the plant Capsella
rubella, was found to produce (À)-caprudiene A (146), (À)-caprutriene B (147),
and (+)-caprutriene C (148) (Fig. 106) [136]. Compound 146 possesses a 6/6/7/5membered ring system, while 147 and 148 have 6/11/5-membered ring systems. In
addition to 146–148, this enzyme also produces (+)-brassitetraene A (149) and (+)brassitetraene B (150) with 15/5-membered ring systems. In fact, 149 and 150 are
considered as intermediates of 146–148. Thus, after the formation of 149 and 150
starting from geranylfarnesyl diphosphate (8), a second round of cyclization,
144
145
Fig. 104 Structures of (þ)-thalianatriene (144) and caprutriene (145)
OPP
H
8
H
144
OPP
OPP
8
110
111
112
(Z)
145
H
11/5-membered
ring system
11/5-membered
ring system
15/5-membered
ring system
Fig. 105 Formation of 144 and 145, and comparison with those of 110–112
Sesterterpenoids
59