Chemistry Reference
In-Depth Information
O
Aux
X
1
X = O, N-(CO)R
R
1
+
Lewis acid
a
R
1
= R
2
= R
3
= H
R
2
b
R
1
= Me
R
2
= R
3
= H
6
c
R
1
= R
2
= H
R
3
= Me
R
3
d
R
1
= H
R
2
= R
3
= Me
2
O
4
5
3
O
O
R
1
O
∗
Aux
X
∗
R
2
∗
Aux
X
∗
∗
∗
R
3
Aux
X
O
Aux
X
O
Aux
X
O
endo-
7
endo-
8
endo-
9
endo-
10
endo-
11
Scheme 4.1
Diels-Alder reactions of auxiliary-modified dienophile
1
with dienes
2-5.
D-glucose
1.) H
2
, Pd/C
2.) 2. NaOMe, MeOH
3.) Ph-CHO, HBF
4
4.) NaH, BnBr
>90%
>90%
92%
95
%
3 steps
HO
HO
AcO
AcO
O
Ph
O
O
O
O
HO
O
AcO
Bn
OH
OH
12
13
14
O
1.) HOAc, H
2
O
2.) PivCl, pyridine
3.) H
2
, Pd/C
78%
97%
quant
.
D-
gluco
Cl
PivO
PivO
PivO
PivO
Et
3
N
O
O
HO
O
83%
15
O
16
L-rhamnose
acetylated rhamnal
3 steps
1.) H
2
, Pd/C
2.) NaOMe, MeO
H
OH
OH
H
3
C
H
3
C
H
3
C
O
O
O
HO
AcO
HO
HO
85% over
2 steps
HO
AcO
17
18
19
O
L-
rhamno
1.) Et
3
N
Cl
45%
H
3
C
O
2.) PivCl, pyridine
quant
PivO
O
O
20
Scheme 4.2
Preparation of d-
gluco
- and l-
rhamno
-configured acrylic esters
16
and
20
as
dienophiles for asymmetric Diels-Alder reactions.
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