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C
8
F
17
C
8
F
17
O
O
L*=
O
Ph
N
N
+
Ph
CO
2
R*
OR
+
Ph
CO
2
R*
Rh
2
(OAc)
4
or CuL*
20
N
2
cis
-19a-e
trans
-18a-e
17a-e
D-
gluco
D-
fructo
D-
ribo
O
O
OMe
O
O
O
O
O
O
O
O
O
O
O
17b
17c
17a
R*
D-
fructo
O
D-
fructo
O
O
O
O
O
O
O
O
O
17e
17d
Scheme 5.5
Diastereoselective metal-catalyzed cyclopropanation of sugar tethered
diazoacetates.
Table 5.4
Stereoselectivities in the cyclopropanation of
17a-e.
Entry
Diazoacetate
Catalyst
Yield (%)
Trans : cis
ratio 22 : 23
18 (% de)
19 (% de)
1
17a
Rh
2
(OAc)
4
20
86 : 14
60
46
2
17a
20,
CuOTf
30
95 : 05
60
53
3
17b
Rh
2
(OAc)
4
21
72 : 28
20
26
4
17b
20,
CuOTf
25
80 : 20
19
26
5
17c
Rh
2
(OAc)
4
35
68 : 32
<
10
<
10
6
17c
20,
CuOTf
62
75 : 25
<
10
<
10
7
17d
Rh
2
(OAc)
4
62
85 : 15
33
12
8
17d
20,
CuOTf
35
96 : 04
34
02
9
17e
Rh
2
(OAc)
4
37
80 : 20
17
68
10
17e
20,
CuOTf
15
85 : 15
2
92
d-ribose. In all cyclopropanations of
-diazoacetates
17a-e
, the chiral catalysts
20-
Cu(I) gave a better
trans/cis
ratio than reactions performed with the achiral
Rh(II) catalyst, showing the prominent role of the bis-oxazoline on this selectivity.
Nevertheless, the similar diastereomeric excess obtained for each of the main
adducts
18a-d
(Table 5.4) with both systems demonstrates the effective and
α
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