activity (Fig. 9). After the formation of 15 via 7 and 14, these tailoring enzymes
apparently convert 15 to 13 [14].
2.2 Definition of “Sesterterpenoids”
The terpenoids are classified by the chain lengths of the polyprenyl diphosphates
used in their biosynthesis. In the case of the sesterterpenoids, they are defined as
compounds that are biosynthesized via geranylfarnesyl diphosphate (GFPP) (8)
(Fig. 10).
For example, preasperterpenoid A (16) is biosynthesized via 8 (Fig. 11) [9]. Thus,
16 is a sesterterpenoid. Actually, 1 is also a sesterterpenoid, while 2 is not, by
considering their biosynthesis pathways (Figs. 6 and 7). Compounds 9–15 are also
not sesterterpenoids (Figs. 8 and 9).
The other classes of terpenoids biosynthesized via different polyprenyl diphosphates are defined as follows: “hemiterpenoids” are from (C 5 ) 3 or 4,
“monoterpenoids” are from (C 10 ) 5, “sesquiterpenoids” are from (C 15 ) 6,
OPP
OPP
OPP
O
H
HO
HO
OH
NH 2
O
O
O
O
OH
O
O
HO
HO
NHAc
HO
O
O
HO
OPP
OPP
H +
3
4
7
14
15
prenyltransferase
oxidase
type 2 terpene cyclase
tailoring enzymes:
prenyltransferase, oxidase,
aminotransferase, methyltransferase,
sugartransferase, and ligase
13
Fig. 9 Putative biosynthesis pathway of brasilicardin A (13). The functional groups of 13, which
might be generated by the tailoring enzymes, are shown in red
Sesterterpenoids
7