Biomedical Engineering Reference
In-Depth Information
TBSO
TBSO
TBSO
H
H
H
O
O
O
O
O
H
O
(Me
3
Si)
3
SiH, AIBN
O
O
•
O
S
S
Si(SiMe
3
)
3
S
Si(SiMe
3
)
3
H
Benzene, reflux, 8 h
38%
O
O
MeO
MeO
MeO
O
•
MeO
MeO
MeO
OMe
OMe
OMe
260
261
262
HO
TBSO
H
H
O
O
H
O
H
O
steps
O
O
H
H
O
O
MeO
OMe
MeO
OMe
OMe
OMe
(+)-Podophyllotoxin
264
263
SCHEME 9.44
Synthesis of podophyllotoxin
264
by Sherburn and coworkers.
workup produces lactone
263
in 38% yield. This compound is then taken through to
(
).
Sherburn and coworkers also prepared the naturally occurring lignans (
)-(7
S
)-
7-hydroxymatairesinol and (
)-(7
S
)-7-hydroxyarctigenin using a similar route [103].
The antipyretic and hypotensive activities of (
þ
)-podophyllotoxin (
264
), which was
isolated from the Chinese ornamental orchid
Dendrobium nobile
, make this tertacyclic
alkaloid an attractive target. Cassayre and Zard explored a domino radical sequence to
this alkaloid starting from (
)-dendrobine (
270
(Scheme 9.45) [104]. In the
early stages of their synthesis, treatment of the enantiomerically pure
þ
)-
-pinene derivative
265
a
with tri-
butyltin hydride and 1,10-azobis(cyclohexanecarbonitrile) (ACCN) led to the expected
265
Me
N
O
Ph
•
•
Bu
3
SnH, ACCN
Toluene, 110°C
71%
MeN
NMe
O
O
O
O
O
O
O
266
267
265
H
Me
N
Me
N
NMe
steps
O
O
H
H
O
O
O
•
O
(-)-Dendrobine
270
269
268
SCHEME 9.45
Cassayre and Zard's synthesis of dendrobine (
270
).
Search WWH ::
Custom Search