Polysaccharide debenzylation

The molecular weight of the debenzylated polysaccharide was estimated to be 2,800 by GPC measurements with water eluent. This value is in very good agreement with the calculated value (2,600) based on the molecular weight of polysaccharide 2 before the debenzylation. The debenzylated... 

Note that in this example the ester was not reduced. When the TBDMS group was replaced with an acetate, the benzyl cleavage reaction failed. The reducing end hemiacetal of a polysaccharide is maintainable during a Birch debenzylation. ... 

The recovery of the deblocked polysaccharide may be most conveniently achieved by sodium in liquid ammonia. Usually, deblocking is accompanied by chain scission, but this is negligible under proper conditions. For example, debenzylation of a polymer with DPn close to 900, which requires the removing of 2700 benzyl ether functions, causes a three- to four-fold decrease in DPn 20,21 Sterically pure linear polysaccharides with a number average degree of polymerization of 150-300 can be prepared by cationic polymerization of ether derivatives of 1,6-anhydro sugars followed by deblocking. 

A conventional method of debenzylation of synthetic polysaccharide derivatives is reduction with sodium in liquid ammonia.24 a solution of benzylated polysaccharide in a toluene/l,2-dimethoxyethane mixture was stirred with an excess amount of liquid ammonia at -33 C. Small pieces of sodium were added gradually to generate solvated-electrons, a powerful reducing agent, in liquid ammonia layer. As debenzylation proceeded, the resulting polysaccharide became soluble in liquid ammonia and debenzyla-... 

The conventional debenzylation was unsuccessful for octadecylated polysaccharide, probably because both the reactant and product were highly lipophilic and hence incompatible with the reducing agent and inorganic solvent. Another debenzylation method via radical bromination and hydrolysises was successfully performed. ee method was effective... 

Monomer [9] was polymerized with 20 mol% phosphorus pentafluoride as initiator in dichloromethane at -78°C for 6 min and the corresponding polymer was obtained in 67% yield. Its conventional debenzylation yielded a comb-shaped polysaccharide [P9] of DPn = 40. 

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