Biomedical Engineering Reference
In-Depth Information
OMOM
OMOM
O
Et
O
5
7
N
N
o
-Cl
2
C
6
H
4
, 140°C, 20 h
OBn
N
N
N
R
R
Diels-Alder
Et
O
O
N
N
N
OBn
CO
2
Me
Me
Me
CO
2
Me
314
315
retro-[3+2]
-N
2
OMOM
MOMO
O
O
O
N
N
7
N
R
steps
R
5
[3+2]
R
Et
Et
Et
OH
O
O
N
N
N
OAc
CO
2
Me
OBn
CO
2
Me
OBn
3
H
H
Me
Me
Me
CO
2
Me
Vindoline (R = OMe,
318
)
Vindorosine (R = H,
319
)
317
(dr = 6-10:1)
316
SCHEME 9.55
Asymmetric synthesis of vindoline
318
and vindorosine
319
by Boger and
coworkers.
[4
2]-cycloadduct. The same approach was also used by the Boger group in their
synthesis of racemic aspidoalbidine and 1-acetylaspidoalbidine [123].
þ
9.6. PHOTOCHEMICALLY INDUCED DOMINO
REACTIONS
The use of photochemically induced domino reactions for the enantioselective
synthesis of biologically active compounds has not been exploited so far. Thus, we
did not find any publication dealing with this topic.
9.7. TRANSITION METAL-CATALYZED DOMINO
REACTIONS
9.7.1. Pd-Catalyzed Domino Reactions
Scopadulcic acids A (
) and B are pharmacologically active constituents found in
the herb
Scoparia dulcis
L. native to many tropical countries. These two natural
products and structurally related derivatives have a wide range of exceptional
biological activities, including
in vitro
and
in vivo
antitumor activities shown in
various human cell lines as well as reported antiviral activity against herpes simplex
virus type 1. In 1999, Overman and coworkers reported an enantiodivergent synthesis
of (
327
) using a Pd-catalyzed domino reaction
(Scheme 9.56) [124]. As substrate for the domino reaction, vinyl iodide
þ
)- and (
)-scopadulcic acid A (
327
324
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