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O
O
O
TiCl
4
, CH
2
Cl
2
+
LDA/ heptane/ THF
HO
O
O
HO
O
O
HO
O
O
C
6
H
5
-C
2
H
5
/ CH
3
CHO
Aldol Reaction -78
°
C
O
O
O
HO
HO
(±)-
53
(±)-
54
7
Lipase AK
Vinyl acetate
40 °C 24h
O
O
+
HO
O
O
HO
O
O
O
O
CH
3
COO
HO
(-)-
56
(+)-
55
54% yield
77% ee
41% yield
ee% not reported
Ph-P/ DEAD
O
NaBH
4
/ CeCl
3
.7H
2
O
Ph
3
PO/ EtOH
O
O
O
-30 °C
O
(+)-
43
63% yield
94 ee%
(+)-calanolide A 94% ee
(+)-calanolide B
A:B=9:1
Scheme 8-11
palladium-catalyzed coumarin formation reaction. The resulting coumarins
angular 48 and linear 47 were a mixture of regioisomers with a ratio of 4 : 1.
The palladium-catalyzed reaction with coumarin (48) and tigloyl methyl carbonate
in the presence of anthracene-based ligand in THF afforded 49, the regiomer
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