Synthesis and X-ray crystal and solution structures of 2,5-anhydro-3,4-O-(1,2-ethanediyl)-D-mannitol: a locked 4T3 furanose conformer

Article abstract of DOI:10.1016/0008-6215(92)84034-P

2,5-Anhydro-3,4-O-(1,2-ethanediyl)-D-mannitol (1) was prepared from 2,5-anhydro-D-mannitol (2) in three steps.The fused ring system was introduced by a phase-transfer alkylation using 1,2-dibromoethane.Its conformation in solution was determined by NMR studies at 500 MHz.Variable-temperature studies showed no lineshape change from 25 to 80 deg in D2O.The data indicate that the five-membered ring is locked by the trans-fused six-membered 1,4-dioxane ring into a twist ⁴T₃ conformation.A single-crystal X-ray study was carried out.The crystals are orthorhombic,C222₁, a = 4.7252 (6), b = 14.0364 (12), c = 13.268 (2) Angstroem, Z = 4, with R = 0.032 for 894 observations.The molecule lies upon a crystallographic two-fold axis, and thus the five-membered ring exists in a perfect ⁴T₃ conformation with a pseudorotation angle of 0 deg and amplitude of 47.2 deg, in agreement with the NMR results.We have shown earlier that, among twenty possible conformers, phosphofructokinase acts specifically an the ⁴T₃ conformer of the β anomer of D-fructose 6-phosphate.