Glucitol 2,5-anhydro-6-chloro-6-deoxy

Tri-0-acetyl-l,5-anhydro-2-deoxy-D-arabino-hex-l-enitol (tri-O-acetyl-D-glucal) was the starting point for the synthesis of 1,5-anhy-dro-2-chloro-2-deoxy-D-glucitol or -D-mannitol by way of the 1,2-dichloride (22), which was reduced32 by means of lithium aluminum hydride to the 2-chloro-2-deoxy derivative (23). That the chlorine... 

Treatment of l,4 3,6-dianhydro-D-glucitol with boron trichloride gives l,6-dichloro-l,6-dideoxy-D-glucitol (20). Although methyl 6-chloro-6-deoxy-a-D-glucopyranoside (isolated as the tribenzoate) could be isolated from the reaction of methyl 3,6-anhydro-a-D-glucopyranoside with boron trichloride (21), the application to the isomeric furanoside derivative led to complex results. 

The presence of the hydrofuran ring also may alter drastically the stability of acetal substituents. For example, the benzylidene acetal moiety, normally stable to alkali, is removed from 3,5-0-benzylidene-6-chloro-6-deoxy-l,4-anhydro-D-glucitol when the compound is heated in alkaline or neutral solution (75). Similarly, l,4 3,6-dianhydro-2,5-0-methylene-D-mannitol loses its methylene group upon heating in aqueous solution (76). 

The direct regioselective chlorination of unprotected hexitols and pentitols by Vilsmeier-Haack reagent (Me2N =CHCl Cl ) has been described For example, D-glucitol was converted, (following acetylation) into 5. Some 2,3,5-tri-6>-acetyl-l,4-anhydro-6-chloro-6-deoxy-D-glucitol was also formed. 

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