3,4- Di-O- acetyl-2,5-anhydro-1,6-dideoxy-1,6-diiodo- d-mannitol ( 3) is prepared from 2,5-anhydro- d-mannitol ( 1) in three steps. The solution and solid-state NMR spectra of 3 indicate considerable variation in conformation. In solution, it adopts, on average, a symmetric 4 T 3 conformation, whereas in the solid state in adopts an asymmetric conformation as revealed by 13C NMR cross polarization and magic angle spinning techniques. A single-crystal X-ray structure analysis confirmed the asymmetric conformation of 3 in a monoclinic crystal, space group P2 1 with a = 8.9608(4), b = 8.6348(5), c = 9.6468(4) A ̊ , β = 96.139(4)°, V = 742.1(1) A ̊ 3 , D c = 2.085g cm −3 , μ ( MoK α) = 4.2 mm −1 , and Z = 2. The structure was refined to R= 0.039 and R w = 0.047 for 5181 observed reflections. The furanoid ring of 3 adopts an envelope E 5 conformation slightly distorted towards 4 T 5, with puckering parameters ϕ = 313.49° and q = 0.37 A ̊ . The asymmetric conformation is rationalized in terms of the weak packing forces in the crystal.