Biomedical Engineering Reference
In-Depth Information
PMPO
PMPO
1. Cp
2
TiMe
2
, THF, 65°C
2. Me
2
AlCl, CH
2
Cl
2
77%
O
O
(-)-Spongistatin 1
O
O
O
H
H
H
H
1. Cp
2
TiMe
2
, Me
3
CCO
2
Et, THF, 65°C
2. Me
2
AlCl, 4 A MS, CH
2
Cl
2
, rt
65%
OTIPS
OTIPS
OO
O
(-)-Clavosolide A
O
OTIPS
O
OTIPS
H
Br
1.
-PrOTMS, TMSOTf, CH
2
Cl
2
, -78°C
2. Cp
2
TiMe
2
, THF, 65°C
65%
i
OMe
O
O
Br
+
OMe
OH
BTSO
O
OMe
O
OH
BTSO
OMe
Me
2
AlCl, CH
2
Cl
2
, rt
O
Br
(-)-Kendomycin
OMe
85%
O
BTSO
OMe
Br
OBPS
Br
OBPS
1. Cp
2
TiMe
2
, THF, 65°C, 19 h
2. Me
2
AlCl, CH
2
Cl
2
, -78°C to rt
42%
H
H
H
H
O
O
(+)-Zampanolide
O
O
O
SCHEME 8.23
Intermediates prepared via Petasis-Ferrier rearrangements.
in Scheme 8.24 [138]. Interestingly, the obvious interest of this synthetic transfor-
mation remained unexplored and neglected up until the late 1980s, when Hopkins and
Overman observed a related transposition when subjecting an allylic acetal to a Lewis
acid that afforded the corresponding acyl tetrahydrofuran (Scheme 8.24) [139].
The Prins-pinacol rearrangement is highly stereoselective and results in the
formation of two C-C bonds, one C-O bond, and two new stereogenic centers. This
K-10 clay
Acetone, reflux
-H
2
O
Prins
cyclization
Pinacol
rearrangement
OHC
OH
HO
HO
O
O
O
OH
Mousset and Martinet
OSnCl
3
OSnCl
3
+
O
Prins
cyclization
Pinacol
rearrangement
-SnCl
4
SnCl
4
CH
2
Cl
2
, -70°C to 0°C
O
+
O
O
O
Cl
O
Cl
Overman and Hopkins
SCHEME 8.24
Selected Prins-pinacol rearrangements.
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