Structures of rac-2,4:3,5-di­methyl­ene xylitol ­derivatives

The structures of three racemic (tetra­hydro-[1,3]dioxino[5,4-d][1,3]dioxin-4-yl)methanol derivatives are reported, namely, 4-[(methyl­sulfon­yloxy)meth­yl]-2,4,4a,6,8,8a-hexa­hydro-[1,3]dioxino[5,4-d][1,3]dioxine, C(8)H(14)O(7)S, 1, 4-[(benz­yloxy)meth­yl]-2,4,4a,6,8,8a-hexa­hydro-[1,3]dioxino[5,4-d][1,3]dioxine, C(14)H(18)O(5), 2, and 4-[(anilinocarbon­yl)meth­yl]-2,4,4a,6,8,8a-hexa­hydro-[1,3]dioxino[5,4-d][1,3]dioxine, C(14)H(17)NO(6), 3. Mesylate ester 1 at 173 K has triclinic P [Image: see text] symmetry and both benzyl ether 2 at 173 K and phenyl urethane 3 have monoclinic P2(1)/c symmetry. These structures are of inter­est because of the conformation of the cis-fused tetra­oxadeca­lin ring system. This cis-bi­cyclo­[4.4.0]decane ring system, i.e. cis-deca­lin, can undergo conformational equilibration. In the two most stable conformers, both six-membered rings adopt a chair conformation. However, there are significant consequences in these two stable conformers, with heteroatom substitution at the 1,3,5,7-ring positions as described. Only one conformation, denoted as ‘concave’ or ‘inside’, is found in these crystal structures. This is consistent with previously reported structures of the 1,1-geminal dihy­droxy aldehyde and tosyl­ate analogs.