Chemistry Reference
In-Depth Information
performed by Stoodley and coworkers. At the outset, they prepared a carbohydrate
analog (
-
119
) of Danishefsky's diene [25] (Scheme 4.18): reaction of acetobromo-
glucose (
116
) and sodium enolate (
117
) gave
β
β
-glucoside
118,
which was converted
into the desired diene (
β
-
119
) [26].
from D-glucose
AcO
O
AcO
OTMS
AcO
TMSCl, ZnCl
2
benzene
78%
AcO
AcO
AcO
Br
DMSO
D-gluco
116
O
O
AcO
AcO
O
O
OTMS
+
AcO
AcO
O
31%
AcO
AcO
OAc
β−
119
O
Na
O
118
119
O
O
OAc
117
OAc
OAc
Scheme 4.18
Preparation of anomeric
β
-gluco diene
β
-
119
from acetobromoglucose
116.
This diene was employed in diastereoselective Diels-Alder reactions with several
cyclic dienophiles (Table 4.5). Out of the possible stereoisomers, reaction of
β
-
119
Table 4.5
Diels-Alder reactions of carbohydrate-derived diene
119
with cyclic dienophiles.
D-gluco
OTMS
O
O
O
H
H
O
OTMS
OTMS
+
O
benzene
OAc
+
R
1
AcO
R
1
R
1
b
-
GD
O
O
O
O
O
AcO
OAc
β
-D-gluco
β
-D-gluco
Entry
Dienophile
Major product
dr (major/minor)
raw product
Isolated yield (major
product) (%)
O
O
O
O
H
OTMS
O
O
1
75 : 25
43
H
O
O
O
β
-D-gluco
O
O
120
121
R
1
=
H
O
O
2
89 : 11
46
H
a
OTMS
R
1
=
CO
2
Et
b
3
88 : 12
75
R
1
R
1
R
1
=
Ac
O
O
123
β
-D-gluco
O
4
75 : 25
43
c
122
X
=
N-Ph
a
O
O
H
5
86 : 14
58
OTMS
X
X
X
=
NH
b
6
85 : 15
37
H
O
O
124
O
125
β
-D-gluco
X
=
O
7
Approx. 6 : 1
52
c
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