Martina Morf

Crystal and molecular structures of d-glycero-d-manno-heptitol (α-sedoheptitol, volemitol) and d-glycero-d-gluco-heptitol (β-sedoheptitol)

Abstract The molecular structures of the title heptitols were determined by X-ray crystallography, using direct methods, and refined to final residual parameters of R = 0.037 and 0.039, respectively. Each compound adopts a bent conformation. For α-sedoheptitol ( 1 ), this is not the expected conformation (with O-6 in the extended planar position). Instead, 1 adopts a conformation with a 1,3- parallel interaction between O-4 and C-7.

The crystal and molecular structures of the hexitol hexa-acetates

Abstract The structures of the 1,2,3,4,5,6-hexa-acetates derived from allitol, galactitol, d - and dl -mannitol (conglomerate and racemate), d - and dl -glucitol, and dl -altritol have been determined by X-ray crystallography, using direct methods, and comprise a complete set of solid-state structures. Compared with the parent alditols, the hexa-acetates have much greater freedom to adopt conformations which involve 1,3-parallel interactions of oxygen and carbon atoms. Such interactions of acetoxyl groups do not impose dominating steric constraints. Parallel alignment of the flat acetoxyl groups can result in the thermodynamically most favoured dense packing of molecules in the crystal.

1,3-Parallel O/ /O interactions in acyclic carbohydrates: the crystal and molecular structures of meso-d-glycero-l-altro-heptitol and the monohydrate, meso-d-glycero-l-ido-heptitol, and meso-d-glycero-l-altro-heptitol and d-glycero-l-galacto-heptitol heptaacetates

Abstract The molecular structures of the title compounds were determined by X-ray crystallography, using direct methods, and refined to final conventional residual parameters of R = 0.042, 0.035, 0.060, 0.062, and 0.047, respectively. meso - d - glycero - l - altro -Heptitol crystallised usually as a monohydrate from moist ethanol with single molecules occurring in the crystal as a racemate of chiral conformers adopting a planar zigzag conformation. Thus, a 1,3-parallel O-3/ /O-5 interaction is tolerated with a distance of 265.0 pm. By thorough exclusion of water, an unhydrated morph was obtained from ethanol and investigated at 173 K. The conformations of single molecules parallel those observed in the hydrate. The O-3–O-5 distance is 267.6 pm. Molecules of the derived heptaacetate avoid this interaction by bending to a sickle, but tolerate, instead, an O-3/ /C-6 relationship with a distance of 295.0 pm. Also, in this case, chiral conformers are observed, which are matched by their enantiomers in the unit cell. meso - d - glycero - l - ido -Heptitol is found in a doubly bent chiral conformation which is free of 1,3-parallel interactions and resembles that found in iditol hexaacetate, but not in iditol itself. Again, a racemate of conformers is observed in the unit cell. The molecules of the heptaacetate of chiral d - glycero - l - galacto -heptitol are found in a sickle conformation, free of 1,3-parallel interactions, a situation already observed for the parent alditol but which could not have been predicted from recent investigations of the solid state structures of other alditol acetates. The occurrence of 1,3-parallel O/ /O interactions in alditols and other acyclic carbohydrates is discussed comprehensively.

The crystal and molecular structures of the pentitol penta-acetates

Abstract The crystal structures of the 1,2,3,4,5-penta-acetates of ribitol, xylitol, and d - and dl -arabinitol have been determined. A modification (mp 50°, space group P 1 − ) of xylitol penta-acetate was investigated, which is not that (mp 65°, space group P21/c) usually encountered.

The crystal and molecular structures of 1,2,3,4,5,6,7,8-octa-O-acetyl-l-threo-l-altro- and -l-threo-l-galacto-octitol

Abstract The molecular structures of the title octitol octa-acetates were determined by X-ray crystallography, using direct methods, and refined to final residual parameters of R = 0.076 and 0.047, respectively. The l - threo - l - altro isomer adopts a bent conformation in which a 1,3-parallel interaction between O-3 and C-6 is tolerated. For the l - threo - l - galacto isomer, a planar zigzag conformation is observed, in which four pairs of oxygen atoms are aligned 1,3 parallel.

The crystal and molecular structure of threitol

Abstract The structure of threitol, C 4 H 10 O 4 , was determined on a crystal of l -threitol at 293 K. This investigation covers also the racemate, because threitol is one of the rare examples that crystallizes as a conglomerate of the pure enantiomers. In disagreement with a recent publication [Jeffrey and Huang, carbohydr. Res. , 223 (1992) 11–18], the space group of l -threitol is P 3 2 with nine molecules in a unit cell of a = 1755.6(1), c = 487.9(1) pm. Crystals of threitol are found as twins by merohedry with a chemically equivalent molecules. The final conventional R factor is 0.032 for all 3628 symmetry-independent reflections. The molecule have the straight carbon-chain conformation, but do not show C 2 symmetry as was claimed previously. This fact confirmed by solid state 13 C CP/MAS NMR experiments.

Kristall- und molekülstruktur von d-arabinitol

Abstract The crystal structure of d -arabinitol[C 5 H 12 O 5 ; space group P 1; a = 482.3(1), b = 767.5(1), and c = 970.5(1) pm; α = 96.13(1), β = 96.04(1), and γ = 106.82(1)°] has been determined by direct methods. The two independent molecules in the asymmetric unit adopt extended zig-zag conformations but differ in the orientation of OH-1.

Die kristall- und molekülstrukturen von drei thermodynamisch benachteiligten 2,6-anhydronitroalditolen (“Glycopyranosylnitromethanen”)

Abstract In extension of previous work, the crystal structures of three thermodynamically less favoured anhydronitroalditols, two of them as acetylated compounds, i.e. , 2,6-anhydro-7-deoxy-7-nitro- d - glycero - l - gulo -heptitol (“α- d -glucopyranosylnitromethane”), 1,3,4,5-tetra-O-acetyl-2,6-anhydro-7-deoxy-7-nitro- d - glycero - d - manno -heptitol (“α- d -mannopyranosylnitromethane tetraacetate”), and 3,4,5-tri- O -acetyl-2,6-anhydro-1-deoxy-1-nitro- d - ido -hexitol (“α- d -xylopyranosylnitromethane triacetate”), were determined by X-ray diffraction using direct methods. This allowed a comparision of the bond lengths and angles at the anomeric centre of “glycopyranosylnitromethanes” with axial vs. equatorial orientation of the nitromethyl group, which gave evidence for an “anomeric effect” of the nitromethyl group.

The crystal and molecular structures of four heptitol heptaacetates

Abstract The structures of the four 1,2,3,4,5,6,7-heptaacetates derived from d - glycero - d - galacto -heptitol and its racemate, d - glycero - d - manno -heptitol, and meso-glycero-gulo -heptitol have been determined by X-ray crystallography using direct methods. The latter two substances are found in conformation that involve a 1,3-parallel O//O interaction.

Crystal and molecular structures of d-glycero-l-gulo-heptitol, meso-glycero-allo-heptitol, and meso-glycero-allo-heptitol heptaacetate

Abstract The molecular structures of the title compounds were determined by X-ray crystallography using direct methods, and refined to final residual parameters of R = 0.040, 0.063, and 0.044, respectively. All the compounds investigated adopt bent conformations, the molecules of meso configuration thus becoming chiral conformers. For meso - glycero - allo -heptitol, this involves a 1,3-parallel interaction between C-5 and O-2. The derived heptaacetate is found in a different conformation with O-3/C-6 and O-4/C-7 aligned 1,3-parallel. The reported solution for meso - glycero - allo -heptitol is conventional, but with regard to the optimum in crystallography has to be considered as preliminary.