Biomedical Engineering Reference
In-Depth Information
CO
2
H
H
2
(20 mol%)
1. NaBH
4
EtOH
I
I
NHPh
I
PhNO
DMSO
O
OH
O
O
OH
2. Zn, AcOH
EtOH
Me
Me
Me
H
H
129
130
77% (3 steps)
131
(ee = 99%)
BrMg
10
OTBS
Me
OH
OPMB
MeO
OH
Me
13
132
OTBS
O
O
Me
Me
H
Me
Me
CO
2
Me
O
Me
H
OMe
2
O
21
O
H
H
OH
MgBr
2
·OEt
2
CH
2
Cl
2
, -78°C
MeO
10
O
O
α
-Aminoxylation
Me
13
Cl
OTBS
Callipeltoside C (
19
)
Me
5
Me
2
CO
2
Me
O
H
OMe
HO
10
OTBS
9
OPMB
Me
13
C1-C14 unit
133
SCHEME 6.27
Synthesis of the C1-C14 unit of callipeltoside C via
a
-aminoxylation.
6.3.3.
-Amination
The direct
a
-amination of carbonyl compounds has been achieved the nucleo-
philic addition to N=N double bonds of diazocarboxylates. List, for example,
reported a proline-catalyzed
a
a
-amination of aldehydes to produce hydroxy
amines such as
quantitatively and with an excellent enantioselectivity
(Scheme 6.29) [56]. Jørgensen and coworkers independently obtained the same
results and showed that asymmetric ketones afforded regioisomeric mixtures such
as
141
142
and
143
[57].
is a
Lycopodium
alkaloid that consist of a fused tetracyclic ring
system containing an aminal moiety (Scheme 6.30) [58]. Takayama and coworkers
demonstrated that the
a
-amination of chiral aldehyde
Cernuine
144
145
catalyzed by diarylprolinol
derivative
ent
-
followed by reduction and cyclization under basic condition
afforded the cyclic carbamate
76
146
in high yield and good diastereomeric excess
(Scheme 6.30). Reductive nitrogen-nitrogen bond cleavage of the latter followed by
various transformations afforded dienone
148
, which was eventually engaged in a
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