218
5.12 Synthesis of Ligularone and Isoligularone
Koike et al. prepared ligularone (168) and isoligularone (1131) starting from an
intermolecular Diels-Alder reaction of silyl enol ether 1128 with 2-methylcyclohex- 2en-1-one (1112) (Scheme 15) [327]. Diketone 1129 thus obtained was converted to
ligularone (168) and isoligularone (1131) via diketone 1130.
A Diels-Alder reaction for construction of a cis-1,2-dimethyl moiety was again
used by Kraus et al. (Scheme 16) [328]. A boron trifluoride ethrate-catalyzed reaction of diene 1132 and aldehyde 1102 afforded a bicyclic alcohol 1133. Isoligularone
(1131) was prepared using ketone 1134 as an intermediate.
TMSO
O
O
O
O
O
O
O
O
168 (ligularone)
O
O
1131 (isoligularone)
+
+
1128
1112
1129
1130
Scheme 15 Synthesis scheme for ligularone (168) and isoligularone (1131) by Koike et al.
Scheme 14 Synthesis scheme for norketone 1127 and 3β-angeloyloxyfuranoeremophilane (191)
by Hsu et al.
M. Tori and C. Kuroda
5.12 Synthesis of Ligularone and Isoligularone
Koike et al. prepared ligularone (168) and isoligularone (1131) starting from an
intermolecular Diels-Alder reaction of silyl enol ether 1128 with 2-methylcyclohex- 2en-1-one (1112) (Scheme 15) [327]. Diketone 1129 thus obtained was converted to
ligularone (168) and isoligularone (1131) via diketone 1130.
A Diels-Alder reaction for construction of a cis-1,2-dimethyl moiety was again
used by Kraus et al. (Scheme 16) [328]. A boron trifluoride ethrate-catalyzed reaction of diene 1132 and aldehyde 1102 afforded a bicyclic alcohol 1133. Isoligularone
(1131) was prepared using ketone 1134 as an intermediate.
TMSO
O
O
O
O
O
O
O
O
168 (ligularone)
O
O
1131 (isoligularone)
+
+
1128
1112
1129
1130
Scheme 15 Synthesis scheme for ligularone (168) and isoligularone (1131) by Koike et al.
Scheme 14 Synthesis scheme for norketone 1127 and 3β-angeloyloxyfuranoeremophilane (191)
by Hsu et al.
M. Tori and C. Kuroda