Biomedical Engineering Reference
In-Depth Information
HN
H
CO
2
Et
N
CHO
Pd(dba)
2
dppb
H
H
H
N
H
CO
2
H
N
PhMe
reflux
42%
N
CO
2
Me
N
CO
2
Me
CO
2
Me
SH
40%
250
251
252
H
N
CHO
H
N
CO
2
H
H
H
H
Dioxane
reflux
68%
N
CO
2
Me
H
CO
2
t-
Bu
N
CO
2
t-
Bu
Deethylibophyllidine
253
254
SCHEME 13.49
cyclization generated azomethine ylide
259a
, which then cycloadded to the pendant
olefin to give
260a
in 81% yield [92]. Under similar conditions,
258b
and
258c
produced
260b
and
260c
in 72% and 51% yields, respectively. Interestingly,
258d
reacted to produce
261
in 74% yield. Presumably, the increased conformational
flexibility in this system allows a transition state that produces the
trans
-fused product.
In each case, the tricycles were produced as single diastereomers.
O
O
O
O
O
H
H
Glycine
5% aq HCl
CHO
CSA (10 mol%)
PhMe
79%
THF, 80°C
89%
N
N
H
H
Cl
255
256
257
MeO
Ac
HN
HN
N
N
N
H
N
H
Aspidospermidine
Aspidospermine
Quebrachamine
CO
2
Et
EtO
2
C
EtO
2
C
Cl
•HCl
H
N
N
H
2
N
CO
2
Et
N
O
H
H
m
m
i-
Pr
2
NEt
PhMe,
m
H
H
n
n
n
258a
(
n
= 1;
m
= 1)
258b
(
n
= 1;
m
= 2)
258c
(
n
= 2;
m
= 1)
258d
(
n
= 2;
m
= 2)
259a
(
n
= 1;
m
= 1)
259b
(
n
= 1;
m
= 2)
259c
(
n
= 2;
m
= 1)
259d
(
n
= 2;
m
= 2)
260a
(
n
= 1;
m
= 1; 81%)
260b
(
n
= 1;
m
= 2; 72%)
260c
(
n
= 2;
m
= 1; 51%)
261
(74%)
SCHEME 13.50
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