Biomedical Engineering Reference
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H
O
(Ph
3
P)AuCl (10 mol%)
AgBF
4
(10 mol%)
CH
2
Cl
2
/MeOH (10:1)
40°C, 0.16 h
H
steps
HO
H
H
I
I
N
O
TBSO
(+)-Fawcettimine
170
SCHEME 4.49
Synthesis of (
þ
)-fawcettimine by Toste and coworkers.
OSEM
(Ph
3
P)AuCl (2 mol%)
AgBF
4
(2 mol%)
Toluene/MeOH (10:1)
rt, 0.5 h
OSEM
8
O
TIPSO
11
171
94%
8 steps
O
OH
O
O
steps
H
HO
2
C
H
H
OH
8
8
(-)-Platencin
173
11
11
172
SCHEME 4.50
Synthesis of the antibiotic (
)-platencin by Nicolaouand coworkers.
was obtained by implementing a gold-catalyzed 5-
exo
-
dig
cycloisomerization on
alkyne
.
Finally, in a synthetic approach to carbon-bridged medium-sized rings, which
are found in a variety of bioactive natural compounds such as enaimeone A
171
176
and hyperforin
177
, Barriault and coworkers showed that cyclic silylenol ethers of
type
could serve as valuable nucleophilic partners in gold-catalyzed intra-
molecular reactions with an alkyne (Scheme 4.51) [48]. The transformation is
174
O
O
OH
O
H
HO
R
2
O
[(JohnPhos)Au(NCCH
3
)]
+
SbF
6
-
(2 mol%)
CO
2
R
TBSO
R
1
Enaimeone A
176
CO
2
R
Acetone, rt, 3-25 h
O
n
R
2
O
R
1
78-92%
O
n
174
175
HO
Hyperforin
177
SCHEME 4.51
Synthetic approach to carbon-bridged medium-sized rings.
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