Synthesis and structure of 1,4:3,6-dianhydro-2-O-p-tosyl-D-mannitol

Abstract

1,4:3,6-Dianhydro-2-O-p-tosyl-D-mannitol (3) has been isolated from the reaction of 1,4:3,6-dianhydro-D-mannitol (2) andp-toluenesulfonyl chloride (1:2 mole ratio) in pyridine in 19% yield after fractional crystallization. It crystallizes in the orthorhombic space groupP2₁2₁2₁ (Z=4) witha=6.064(2),b=8.347(1) andc=26.455(16) Å. Disorder associated with the unsubstituted furanose ring provides two arrangements, rings B and C, with two sets of sites for both the hydroxyl group and a ring carbon atoms: the relative occupancy of ring B: ring C=0.53(1):0.4791). Distinct H-bonding situations (both intra-and inter-molecular) are associated with the two arrangement. The conformations of the unsubstituted furanose ring with the weaker intramolecular H-bonding (ring B) and the tosyl-substituted ring (ring A) are very similars, being 1:2 mixtures of envelope [³ E] and twist forms [³ T ₄]: the stronger H-bonding in ring C results instead in a conformation made up from a 30:70 mixture ofE ₀ and⁴ T ₀ forms. The¹H-NMR spectrum for3 indicates that the average solution conformation is also a mixture of envelope and twist forms and is similar to that of the A/B solid-state arrangement.