Heteroatom Exchange
2.3
257
⊡ Scheme 60
⊡ Scheme 61
⊡ Scheme 62
timidate 133 undergoes reflux in xylene in the presence of potassium carbonate, giving the
corresponding trichloroacetamide 134 with total stereoselectivity ( > Scheme 61) [100].
In another interesting reaction, 2-azido-2-deoxypyranosyl fluoride 136 is obtained from the
2-OH unprotected mannosyl azide 135, by DAST-mediated displacement involving neighboring group participation and migration of the anomeric azide group ( > Scheme 62) [101].
3.7 Miscellaneous Methods
Under dehydrating conditions, D-fructose 137 will effectively react with amines to produce
the corresponding imine product 138, which can be transformed into the aldohexose 139
by using zinc halide as catalyst. Condensation of 139 with another equiv. of amine followed by ring-closure and hydrolysis gives the 2-alkylamino-2-deoxy-D-glucopyranose 140
( > Scheme 63) [102].
2.3
257
⊡ Scheme 60
⊡ Scheme 61
⊡ Scheme 62
timidate 133 undergoes reflux in xylene in the presence of potassium carbonate, giving the
corresponding trichloroacetamide 134 with total stereoselectivity ( > Scheme 61) [100].
In another interesting reaction, 2-azido-2-deoxypyranosyl fluoride 136 is obtained from the
2-OH unprotected mannosyl azide 135, by DAST-mediated displacement involving neighboring group participation and migration of the anomeric azide group ( > Scheme 62) [101].
3.7 Miscellaneous Methods
Under dehydrating conditions, D-fructose 137 will effectively react with amines to produce
the corresponding imine product 138, which can be transformed into the aldohexose 139
by using zinc halide as catalyst. Condensation of 139 with another equiv. of amine followed by ring-closure and hydrolysis gives the 2-alkylamino-2-deoxy-D-glucopyranose 140
( > Scheme 63) [102].