Biomedical Engineering Reference
In-Depth Information
OTBDPS
MOMO
HO
CHO
OTBDPS
O
i-
PrO
2
C
MOMO
OH
HO
O
O
113
(1.93 equiv)
HO
O
O
Xylenes, BHT
140°C, 5 h
O
CO
2
i-
Pr
H
O
+
69-97%
O
O
O
H
O
MPMO
H
OH
OMOM
(+)-Tetronolide
112
MPMO
H
OMOM
115
114
(0.07 M)
SCHEME 9.21
Synthesis of tetronolide
112
by Boeckmann and coworkers.
PhSO
2
TBS
TBS
TfOH
Zn(OTf)
2
DCE, 96°C, 16 h
O
O
N
PhO
2
S
PhO
2
S
OTBS
54%
N
N
TfO
Zn(OTf)
Zn(OTf)
116
117
118
Ph
Ph
TBS
TBS
O
SO
2
O
SO
2
PhO
2
S
O
O
steps
TfO
N
N
N
N
H
Zn(OTf)
Zn(OTf)
Lycopodine
122
121
120
119
SCHEME 9.22
Synthesis of lycopodine
122
by Carter and coworkers.
116
that leads via
117
-
120
to the desired product
121
in 54% yield; this compound
was further manipulated to give the alkaloid
122
(Scheme 9.22).
9.3.2. Domino Reactions with Aldol Reactions as the
Initiating Step
The methodological development of a diastereoselective aldol/Prins domino reaction
by Rychnovsky and coworkers has also been applied by the same group to the
synthesis of a natural product containing a
cis
-2,6-disubstituted tetrahydropyran
ring system [52]. The target, leucascandrolide A (
) isolated from the sponge
Leucascandra caveolata
exhibits potent cytotoxicity against P388 cancer cells [53].
The two enantiopure starting materials, aldehyde
126
123
and alkyl enol ether
124
, in the
presence of BF
3
OEt
2
underwent a domino reaction to form the bis-tetrahydropyran
125
and two new C-C bonds [54]. The creation of a new stereogenic center at C9 in a
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