MOLECULAR-ORBITAL STUDIES OF BORATE XYLOPYRANOSE CHELATES

The AM1 and AM1/MNDO molecular orbital schemes were used to study the structures of the 1 : 1 and 1 : 2 borate chelates Of D-xylopyranose, According to the calculations the most stable 1 : 1 borate chelate Of D-Xylose is unambiguously the 1,2-borate of alpha-D-Xylopyranose-C-4(1). In the case of the 1 : 2 compounds, the calculations similarly indicate the most stable chelate to be the 1,2-borate of alpha-D-xylopyranose in the C-4(1) conformation. Distinct structural distortions of the xylopyranose ring occur upon chelation at the O1-C1 and O2 C2 positions of the alpha-D-xylopyranose-C-4(1). No corresponding structural distortion was found for the chelate formed at the O1-C1 and O3-C3 positions.