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

Abstract

The title compound, C16H24O10·0.11H2O, is a key intermediate in the synthesis of 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG), which is the most widely used molecular-imaging probe for positron emission tomography (PET). The crystal structure has two independent molecules (AandB) in the asymmetric unit, with closely comparable geometries. The pyranose ring adopts a4C1conformation [Cremer–Pople puckering parameters:Q= 0.553 (2) Å, θ = 16.2 (2)° and ϕ = 290.4 (8)° for moleculeA, andQ= 0.529 (2) Å, θ =15.3 (3)° and ϕ = 268.2 (9)° for moleculeB], and the dioxolane ring adopts an envelope conformation. The chiral centre in the dioxolane ring, introduced during the synthesis of the compound, has anRconfiguration, with the ethoxy groupexoto the mannopyranose ring. The asymmetric unit also contains one water molecule with a refined site-occupancy factor of 0.222 (8), which bridges between moleculesAandB viaO—H...O hydrogen bonds.