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OSiMe
3
OPiv
PivO
OPiv
PivO
81
H
3
CO
R-CHO
4
1. ZnCl
2
Et
2
O
THF/-20 °C
2. NH
4
Cl/H
2
O
O
O
NH
2
OPiv
N
R
PivO
PivO
OPiv
H
3
5
OPiv
PivO
OPiv
PivO
O
N
O
O
N
OCH
3
PivO
PivO
OPiv
OPiv
H
R
H
O
R
82
84
H
+
OPiv
PivO
OPiv
PivO
O
N
O
O
OCH
3
N
PivO
PivO
OPiv
R
OPiv
H
R
O
H
83
85
Scheme 1.25
Diastereoselective synthesis of
N
-galactosyldehydropiperidones
84
and
85.
In 2004, Kunz reported the application of arabinosylamine
10
as a suitable
pseudo
enantiomeric auxiliary to the galactosylamine
3
[38a].
N
-Arabinosylimines
11
react with silyl dienol ether
81
in a domino Mannich-Michael reaction sequence
to give 2-substituted 5,6-dehydropiperidinones
86.
The 2-substituted dehydropipe-
ridinones are formed with opposite stereochemistry compared to those from the
tandem Mannich-Michael reaction with d-galactosylamine as auxiliary (Scheme
1.26).
OSiMe
3
81
PivO
PivO
H
3
CO
PivO
O
OPiv
OPiv
R-CHO
4
OPiv
1. ZnCl
2
Et
2
O
THF/-20 °C
2. 1N HCl
OPiv
OPiv
OPiv
O
NH
2
O
R
N
O
N
H
R
10
11
86
Scheme 1.26
Diastereoselective synthesis of 2-substituted
N
-arabinosyl dehydropiperidinones
86.
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