Modifications of C-6 in Hexopyranoses

For example, the bulky trityl chloride selectively reacts with primary alcohol groups (see section 4.3b). The secondary alcohol groups can then be protected by acetylation or benzoylation, and the trityl group selectively removed by mild acid hydrolysis (see reaction 4.16). The reaction of tosyl chloride has also been used to selectively derivatize the primary alcohols [6]. The tosyl group can then be displaced by various nucleophiles such as halides or azide (reaction 4.14). 

The substitution of a primary hydroxyl group by a halide, can be accomplished directly by reaction with triphenylphosphine and carbontetrachloride or carbonte-trabromide [117]. The direct substitution of iodine can be obtained by reaction of triphenylphosphine, iodine, and imidazole [118]. These reactions are illustrated by the substitution of the primary hydroxyl groups of C-6 and C-6 of sucrose (reactions 4.126). 

The primary hydroxyl group at the C-1 position on the fructose ring of sucrose is much less reactive than the hydroxyl groups at the C-6 and C-6 positions, due 

6 -Dideoxysucrose can be prepared by specifically iodinating the sucrose with triphenylphosphine, iodine, and imidazole [119], followed by catalytic hydrogenation (reaction 4.128). 

The C-6 primary alcohol group of sucrose can be selected by the formation of 4,6-(9-benzilidene sucrose [32] (reaction 4.27). The free hydroxyl groups are then benzoylated and the 4,6-0-benzilidene group is selectively cleaved by reaction with trimethylamine/borane and aluminum chloride in toluene [34] to produce the 

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