252
2
General Synthetic Methods
⊡ Scheme 48
⊡ Scheme 49
3.2 Opening of Epoxide Rings
Nucleophilic ring-opening of epoxides with nitrogen nucleophiles offers another route to
amino sugars. Similar to the above-mentioned nucleophilic substitutions, epoxide openings
can be conducted with ammonia, primary amines, guanidine, or azide ions [17,86]. Ammonium chloride is often used to neutralize the alkoxide produced during the opening of an
epoxide.
3.3 Addition of Nitrogenous Reagents to Double Bonds
3.3.1 Addition to Glycals
Chloronitroxylation of glycal double bonds has been used as a means for synthesizing 2-amino-2-deoxy sugar derivatives. As illustrated in > Scheme 50, the addition of nitrosyl chloride
to tri-O-acetyl-D-glucal 81 gives a dimeric adduct which can be converted into the oxime 99
in high stereoselectivity with alcohols [87]. Reduction of the product provides corresponding
amino sugar derivatives (see > Sect. 3.5).
⊡ Scheme 50
2
General Synthetic Methods
⊡ Scheme 48
⊡ Scheme 49
3.2 Opening of Epoxide Rings
Nucleophilic ring-opening of epoxides with nitrogen nucleophiles offers another route to
amino sugars. Similar to the above-mentioned nucleophilic substitutions, epoxide openings
can be conducted with ammonia, primary amines, guanidine, or azide ions [17,86]. Ammonium chloride is often used to neutralize the alkoxide produced during the opening of an
epoxide.
3.3 Addition of Nitrogenous Reagents to Double Bonds
3.3.1 Addition to Glycals
Chloronitroxylation of glycal double bonds has been used as a means for synthesizing 2-amino-2-deoxy sugar derivatives. As illustrated in > Scheme 50, the addition of nitrosyl chloride
to tri-O-acetyl-D-glucal 81 gives a dimeric adduct which can be converted into the oxime 99
in high stereoselectivity with alcohols [87]. Reduction of the product provides corresponding
amino sugar derivatives (see > Sect. 3.5).
⊡ Scheme 50