Aldohexoses 2.5- anhydro

Aldohexopyranoses, 2-amino-2-deoxy-, deamination of, 184 Aldohexoses, crystallography of, 61 gel chromatography of, 31 —, 2,5-anhydro-, 183... 

For aldohexoses, OH-1, OH-2, and OH-6 seem to be particularly reactive [399,400]. Nevertheless, the initial product of the treatment of D-a/tro-3-heptulose (coriose) with chlorotrimethylsilane in pyridine is claimed to have a free hemiacetal hydroxyl group [401]. 1,6-Anhydro-P-D-glucopyranose yielded 87% of the 2,4-disilyl ether [402],... 

All stereocenters in 1,6-anhydrohexopyranoses are of inverted orientation compared to those in the parent 4Ci(d) or 1C4(l) conformations of the corresponding hexopyranoses for example, see 21, 23, and l,6-anhydro-/J-D-glucopyranose (22). In chemical properties, these compounds resemble to a certain degree the methyl /f-D-hexopyranosides. They are relatively stable in alkaline media, but are readily hydrolyzed by acids. In aqueous acid solution, an equilibrium is established between the 1,6-anhydrohexo-pyranose and the corresponding aldohexose, whose composition correlates with expectations from conformational analysis and calculations from thermodynamic data.121 Extreme values, 0.2 and 86%, are observed respectively with 1,6-anhydro-/f-D-glucopyranose (22) and l,6-anhydro-/f-D-idopyranose (the latter has all hydroxyl groups in equatorial disposition). 

The polynertzatton of unsubstttuted blcycllc acetals promised to be a very good field to study the relationship between ring strain and polynerlzablllty In 1973, when we published the first paper In this series, Schuerch had already described the polymerization of substituted 1,6-anhydro aldohexoses to high molecular weight crystalline polymers ( ). 

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