3,4,6-Tri-O-acetyl-1,2-O-[1-(exo-ethoxy)ethylidene]-β-D-mannopyranose 0.11-hydrate

Abstract

The title compound, C(16)H(24)O(10)·0.11H(2)O, is a key intermediate in the synthesis of 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG), which is the most widely used molecular-imaging probe for positron emission tomography (PET). The crystal structure has two independent molecules (A and B) in the asymmetric unit, with closely comparable geometries. The pyranose ring adopts a (4)C(1) conformation [Cremer-Pople puckering parameters: Q = 0.553 (2) Å, θ = 16.2 (2)° and φ = 290.4 (8)° for molecule A, and Q = 0.529 (2) Å, θ =15.3 (3)° and φ = 268.2 (9)° for molecule B], and the dioxolane ring adopts an envelope conformation. The chiral centre in the dioxolane ring, introduced during the synthesis of the compound, has an R configuration, with the ethoxy group exo to the mannopyranose ring. The asymmetric unit also contains one water molecule with a refined site-occupancy factor of 0.222 (8), which bridges between molecules A and B via O-H···O hydrogen bonds.