Talose, 1,6:2,3-dianhydro

The Action of Alkaline Reagents on 2 3-1 6- and 3 4-l 6-Dianhydro-3-talose. A Constitutional Synthesis of Chondrosamine and other Amino-Sugar Derivatives, S. P. James, F. Smith, M. Stacey, and L. F. Wiggins, J. Chem. Soc., (1946) 625-628. 

Die Desaminierung von Aminozuckern fiihrt in manchen Fallen zu ver-schiedenen Anhydro-Derivaten. Im Falle der 4-Amino-4-desoxy-l,6-anhydro-fl-D-mannopyranose wurde unter Waldenscher Umkehr am C-4 die l,6-3,4-Dianhydro-j3-D-talose erhalten is.nv). 

Moving clockwise around the pyranose ring, the next example is provided by the deamination of 4-amino-1,6-anhydro-4-deoxy-/3-n-mannose (LXXII), which gives 1,6 3,4-dianhydro- 3-D-talose (LXXIII). There is some evidence indicating that the parent compound 1,6-anhydro-/3-D-mannopyranose, which cannot adopt the usual chair conformation (Cl), favors the reverse chair conformation (1C) to the alternative boat form (SB) Thus, we can assume that the above derivative also favors the reverse chair conformation LXXII and that the anhydro sugar is formed through the mechanism involving axial and antiparallel substituents. 

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