Crystal structure and molecular packing analysis of 1,5-anhydropentitols and per-O-acetyl derivatives

The crystal structures of three 1,5-anhydropentitols of formulae C 5 H 10 O 4 and their per-O-acetyl derivatives of formulae C 11 H 16 O 7 are reported. 1,5-Anhydro-D-arabinitol (ADA), 1,5-anhydroribitol (AR), 1,5-anhydroxylitol (AX), 2,3,4-tri-O-acetyl-1,5-anhydro-D-arabinitol (AcADA), 2,3,4-tri-O-acetyl-1,5-anhydroribitol (AcAR) and 2,3,4-tri-O-acetyl-1,5-anhydroxylitol (AcAX) have the following space group and unit cell parameters: ADA, orthorhombic, P2 1 2 1 2 1 , a = 6.521(1) A, b = 6.826(1) A, c = 13.557(3) A; AR, monoclinic, P2 1 /n, a = 6.515(1) A, b = 12.003(1) A, c = 8.272(1) A, β = 105.65(1)°; AX, monoclinic, P2 1 /n, a = 6.652(2) A, b = 9.224(2) A, c = 10.548(2) A, β = 101.80(1)°; AcADA, orthorhombic, P2 1 2 1 2 1 , a = 8.182(2) A, b = 10.768(2) A, c = 15.111(3) A; AcAR, monoclinic, P2 1 /c, a = 15.178(1) A, b = 10.339(1) A, c = 8.038(1) A, β = 92.50(1)°; and AcAX, monoclinic, P2 1 /c, a = 12.092(1) A, b = 9.066(1)A, c = 12.492(2)A, β = 102.39(1)°. The structures were solved using direct methods and refined by full-matrix least-squares techniques to R indices of 0.033, 0.042, 0.045, 0.066, 0.055 and 0.048, respectively. The pyranoid ring adopts 4 C 1 chair conformation in the molecules of AR, AX and AcAX, and the 1 C 4 one in the molecules of ADA, AcADA and AcAR. Theoretical methods were used to examine lattice energetics and molecular packing in the crystals formed.