Biomedical Engineering Reference
In-Depth Information
R
R
R
1. Na/Napht
THF
2. POCl
3
Ts
N
N
Ts
N
AuCl
3
(5 mol%)
CH
2
Cl
2
, rt, 15 h
O
O
Cl
N
N
N
Bn
Bn
Bn
148
146
147
R=H (82%)
R=H (62%)
R=Me (58%)
R=Me (69%)
CO
2
H
CO
2
H
N
N
N
O
N
H
H
H
MeO
HO
NH
2
Lavendamycin
149
O
Harmine
Dichotomine A
SCHEME 4.42
Padwa and coworkers' approach to
b
-carbolines.
R
2
R
2
R
2
O
O
O
(Ph
3
P)AuCl (10 mol%)
AgOTf (10 mol%)
HOAc, 100°C, 1 h
[O]
N
N
H
R
1
R
1
R
1
52-95%
O
O
O
150
151
152
O
N
OH
N
N
N
N
O
O
O
Cleistopholine
153
Sampangine
154
Meridine
155
(60%)
SCHEME 4.43
Synthesis of azaanthraquinones by a Au(I)-catalyzed cycloisomerization of
N
-propargylamino quinones by Wang and coworkers.
possessing a
b
-carboline core and might be directly applied to the synthesis of the
alkaloid lavendamycin
.
A method allowing the formation of azaanthraquinones
149
152
by a gold(I)-
catalyzed cycloisomerization of
N
-propargylamino quinones
150
was recently
developed by Wang and coworkers (Scheme 4.43) [41].
In this process, the nucleophilic enamine group adds onto the gold-activated
alkyne following a 6-
endo
-
dig
cyclization mode to produce intermediate
151
.
The latter was then oxidized to afford the azaanthraquinone
. This transformation
has been successfully applied to the total synthesis of the alkaloid cleistopholine
152
153
and could be also used to access the structurally related alkaloids sampangine
154
and meridine
155
.
4.3.2.2. Other Transformations A few other gold-catalyzed transformations
that differ from the more classical cycloisomerization of enynes or allene-enes have
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