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 C5H10 O4 and their per-O-acetyl derivatives of formulae C11H16O7 are reporte d. 1,5-anhydro-D-arabinitol (ADA), 1,5-anhydroribitol (AR), 1,5-anhydr oxylitol (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 pa rameters: ADA, orthorhombic, P2(1)2(1)2(1), a = 6.521(1) Angstrom, b = 6.826(1) Angstrom, c = 13.557(3) Angstrom; AR, monoclinic, P2(1)/n, a = 6.515(1) Angstrom, b = 12.003(1) Angstrom, c = 8.272(1) Angstrom, b eta = 105.65(1)degrees; AX, monoclinic, P2(1)/n, a = 6.652(2) Angstrom , b = 9.224(2) Angstrom; 10.548(2) Angstrom, beta = 101.80(1)degrees; AcADA, orthorhombic, P2(1)2(1)2(1), a = 8.182(2) Angstrom, b = 10.768( 2) Angstrom, c = 15.111(3) Angstrom AcAR, monoclinic, P2(1)/c, a = 15. 178(1) Angstrom, b = 10.339(1) Angstrom, c = 8.038(1) Angstrom, beta = 92.50(1)degrees; and AcAX, monoclinic, P2(1)/c, a = 12.092(1) Angstro m, b = 9.066(1) Angstrom, c = 12.492(2) Angstrom, beta = 102.39(1)degr ees. The structures were solved using direct methods and refined by fu ll-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 C-4(1 ) chair confirmation in the molecules of AR, AX and AcAX, and the C-1( 4) one in the molecules of ADA, AcADA and AcAR. Theoretical methods we re used to examine lattice energetics and molecular packing in the cry stals formed.