OPP
8
122
H
H
+
H
OHC
O
second-round cyclization
11/5-membered
ring system
oxidation
Fig. 88 Structure of variecolin (122), and possible cyclization reaction for the formation of the 5/8/
6/5-membered ring system of 122
OPP
H
H
H
H
H
8
OH
H 2 O
OH
O
124
O
CHO
123
O
O
OH
HO
HO
H
15/5-membered
ring system
Fig. 89 Structures of aleurodiscal (123) and nitidasin (124), and possible cyclization reaction for
the formation of the 5/8/6/5-membered ring systems of 123 and 124