Ring Conformation in the Schardinger Dextrins

Recently Freudenberg and Cramer have proposed that flexible ring forms intermediate between B1 and 3B are involved in varying degree in the Schardinger dextrins and starch. 

The acetates, nitrates, and methyl ethers of the Schardinger dextrins have been reported in crystalline form. There are over 20 reports on the preparation and properties (for example, the optical rotation) of -dextrin acetate from the work of Pringsheim alone. No attempt can be made to review the entire literature in this field, since most of it is only of historical interest. Rather the most recent or most reliable results will be summarized. 

Judging from reports in the literature and the author s experience, one would think the preparation of the Schardinger dextrin acetates would be nearly fool-proof. Even so, widely varying optical rotations and other properties have been reported for these compounds. As has been seen, the variation in optical rotations, melting points, and freezing-point depression with different dextrin preparations has led to an abundance of confusion in this area. 

A preparative method which works was reported by French and coworkers. 

Leibowitz and Silmann prepared crystalline a- and jS-dextrin di- and tri-nitrates. 

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