256
2
General Synthetic Methods
⊡ Scheme 58
⊡ Scheme 59
which can be hydrogenolyzed to the 3-amino-3-deoxy-α-D-glucopyranoside 128 with a good
stereoselectivity ( > Scheme 59) [97].
3.5 Reduction of Ulose Oximes
Oxime formation from uloses and subsequent reduction provides yet another route to amino
sugars. The stereochemical outcome is dependent on the reducing agent, solvent, and protecting groups [98]. For example, PtO 2 reduction of the oxime 129 gives only the L-ribo derivative 130 with the amino group in an axial orientation, whereas borane reduction of acylated
oxime 131 produces mainly the L-arabino derivative 132 with an equatorial amino substituent
( > Scheme 60) [99].
3.6 Rearrangement Reactions
The rearrangement of allyl trichloroacetimidate into allyl trichloroacetamide (Overman rearrangement) has been used for the synthesis of amino sugars. For example, the trichloroace-
2
General Synthetic Methods
⊡ Scheme 58
⊡ Scheme 59
which can be hydrogenolyzed to the 3-amino-3-deoxy-α-D-glucopyranoside 128 with a good
stereoselectivity ( > Scheme 59) [97].
3.5 Reduction of Ulose Oximes
Oxime formation from uloses and subsequent reduction provides yet another route to amino
sugars. The stereochemical outcome is dependent on the reducing agent, solvent, and protecting groups [98]. For example, PtO 2 reduction of the oxime 129 gives only the L-ribo derivative 130 with the amino group in an axial orientation, whereas borane reduction of acylated
oxime 131 produces mainly the L-arabino derivative 132 with an equatorial amino substituent
( > Scheme 60) [99].
3.6 Rearrangement Reactions
The rearrangement of allyl trichloroacetimidate into allyl trichloroacetamide (Overman rearrangement) has been used for the synthesis of amino sugars. For example, the trichloroace-