Septanoid Sugar Derivatives

The crystal-structure analysis of sugar derivatives having a seven-membered ring have been reported. The X-ray data for 5-0-(chloro-acetyI)-l,2 3,4-di-0-isopropyIidene-a-D-gIucoseptanose (26) showed 

Crystal-structure diagram for 5-0-(chloroacetyl)-142 3,4-di-0-isopropylidene-a-D-glucoseptano e (26). (The numbers given along the bonds are the projected dihedral angles between the atoms attached to the bonded atoms,) 

The conformations of septanoid sugar derivatives in solution have been investigated by n.m.r. spectroscopy. Preliminary evidence points to a chair-like conformation for the septanoid molecule in solution. Such a chair conformation has been observed for D-xylo-4,5,6-trihydroxy-l-methyl-4,5,6,7-tetrahydro-lH- 1,2-diazepin (27) in 

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