Amylose xanthates

Amylose and dextran have been studied in aqueous solution as the xanthate derivatives. Dextran xanthate has no observable c.d., but amylose xanthate in aqueous solution has a complex c.d. that indicates an organized structure. 

Marchessault, Sarko etal. [10, 11] have investigated the chiroptical properties of amylose xanthates extensively. The CD of amylose triacetate in trifluoroethanol shows, apart from the expected acetyl z -> tt transition at about 230 nm, an additional shortwave peak. This is again explained by assuming a helical conformation of the amylose chain. Dextran acetates and mycodextran acetates, on the other hand, do not show conformational effects. The considerable changes in the CD spectra of amylose triacetate films when the temperature increases from 30 to 190°C are particularly remarkable. As X-ray diffraction analysis shows, these effects are connected with crystallisation processes and transformation during annealing. 

Fig. 2. ORD (top) and CD (bottom) of partially substituted potassium salts of dextran xanthate (A) and amylose xanthate (B) [10].

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