Crystal Polymorphism of Methyl 2,3,4-tri-O-acetyl-1-O-(trichloroacetimidoyl)-α-d-glucopyranouronate
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The polymorphism of the glycoside donor methyl 2,3,4-tri-O-acetyl-1-O-(trichloroacetimidoyl)-α-d-glucopyranouronate (1) has been investigated. Two polymorphic forms (labelled Forms I and II) have been elucidated and fully characterised by DSC, PXRD and single crystal analysis, both crystallizing in the space group P21. Form I was obtained by crystallization from a wide range of solvents, while Form II was obtained only from ethyl acetate or isopropanol on certain occasions. Unit cell dimensions for Form I are a 14.0292(12), b 8.9641(8), c 16.8580(14) Å, β 94.285(2)°, and for Form II a 11.266(3), b 6.8889(17), c 13.921(4) Å, β 101.161(6)°. Z’ is 2 for Form I and 1 for Form II. Form I displays two moderate intermolecular hydrogen bonds in the unit cell whereas Form II shows no moderate hydrogen-bonding motifs. All three molecules in the two polymorphs differ significantly in their conformations, especially with respect to the methyl carboxylate and trichloroacetimidoyl groups.
KeywordsMethyl 2,3,4-tri-O-acetyl-1-O-(trichloroacetimidoyl)-α-d-glucopyranouronate Polymorphism Imine hydrogen bonding
This publication has emanated from research conducted with the financial support of Science Foundation Ireland under Grant Numbers 07/SRC/B1158, 08/RFP/MTR1664 and 05/PICA/B802/EC07.
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