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OAc
OAc
O
a
b
O
+
OTBS
OH
OTBS
122
123
124
O
c
d
O
OTBS
OTBS
125
126
OH
3
Reagents and Conditions: (a) i. 122,Ph
3
P, Imid., I
2
, MeCN/Et
2
O; ii. 123,LDA,
78
C; (b) i. K
2
CO
3
,
MeOH; ii. MnO
2
,CH
2
Cl
2
; (c) TiCl
4
, Zn, THF, reflux, 25 h; (d) TBAF, THF.
±
Scheme 6-4
O
a
b
CO
2
Et
CO
2
Et
OH
128
92
127
c
d
HO
CHO
CHO
OH
129 5
Reagents and Conditions: (a) n-BuLi, (EtO)
2
POC(i-Pr)CO
2
Et, THF,
78
C, 60%; (b) SeO
2
, t-BuOOH,
CH
2
Cl
2
, 45%; (c) LiAlH
4
, ether, then BaMnO
4
,CH
2
Cl
2
, 70%; (d) TiCl
3
(DME)
2
/Zn-Cu, DME,
40
C,
then H
2
O, K
2
CO
3
, 46%.
±
Scheme 6-5
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