217
Scheme 13 Synthesis scheme for 6-hydroxyeuryopsin (248), toluccanolide A (434), and toluccanolide C (436) by White’s group
O
O
OTIPS
Br
O
CO 2 H
O
OH
TBS
O
TBS
Bu 3 Sn
OTIPS
O
TBS
O
OH
248 (6-hydroxyeuryopsin)
Pd 2 (dba) 3
AsPh 3
1112
1113
1114
1115
1116
1117
1118
Scheme 12 Synthesis scheme for 6-hydroxyeuryopsin (248) by White’s group
5.11 Synthesis of 3β-Angeloyloxyfuranoeremophilane
Hsu et al. reported that an intermolecular Diels-Alder reaction between α-quinone
derived from 1122 and ethyl vinyl ketone afforded 1123 (Scheme 14) [326]. A
Claisen-type rearrangement of silyl enolate of 1123 produced 1124. A several-step
transformation through 1125 gave norketone 1127. 3β-Angeloyloxyfuranoeremoph
ilane (191) was obtained by another alkylation of 1125 to 1126 and formation of the
furan ring.
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…
Scheme 13 Synthesis scheme for 6-hydroxyeuryopsin (248), toluccanolide A (434), and toluccanolide C (436) by White’s group
O
O
OTIPS
Br
O
CO 2 H
O
OH
TBS
O
TBS
Bu 3 Sn
OTIPS
O
TBS
O
OH
248 (6-hydroxyeuryopsin)
Pd 2 (dba) 3
AsPh 3
1112
1113
1114
1115
1116
1117
1118
Scheme 12 Synthesis scheme for 6-hydroxyeuryopsin (248) by White’s group
5.11 Synthesis of 3β-Angeloyloxyfuranoeremophilane
Hsu et al. reported that an intermolecular Diels-Alder reaction between α-quinone
derived from 1122 and ethyl vinyl ketone afforded 1123 (Scheme 14) [326]. A
Claisen-type rearrangement of silyl enolate of 1123 produced 1124. A several-step
transformation through 1125 gave norketone 1127. 3β-Angeloyloxyfuranoeremoph
ilane (191) was obtained by another alkylation of 1125 to 1126 and formation of the
furan ring.
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…