Figure 1. Thermal ellipsoids and atom numbering for maltose octapropanoate. The ellipsoids indicate the regions within which the probability of finding the nuclei is 50%.

Figure 2. B3LYP/6-31+G(d) and B3LYP/6-311+G(d) energies for various orientations of an ‘anomeric’ acetate group on tetrahydropyran in an equatorial disposition. Both observed orientations in 1 and 2 with H1–C1–O1–C7 = 2.5° and 46.4°, respectively, have low energies.

Figure 3. The experimental geometry of maltose octapropanoate, showing just the two rings, the propanoyl groups located on C3 and C2′, and the distances between several pairs of atoms. The short distances indicate attraction between the propanoyl groups despite a fairly long distance between O3 and O2′.

Figure 4. Experimental (a) C–C and (b) C–O bond lengths from 1 (esterified), averaged with data from glucose pentaacetates and β-maltosylnitromethane heptaacetate, compared with results from B3LYP/6-311+G(d) calculations. Also shown are bond lengths for the native (hydroxyl-bearing) glucose and maltose molecules. All C–C bonds found in the native molecules were included, while C–O bonds were from those attached to the 1, 2, 3, 6, and 2′, 3′, 4′, and 6′ carbons. The diagonal line shows the ideal, on which all points would fall if there were no differences among the structures or computational methods. The shortest bond lengths in each set in (b) are for the C1–O1 bond in the β-configuration.

Figure 5. Crystal packing in 1 (see text). (a) Projection onto the b–c plane with the unit cell shown. C6 and C6′ groups are indicated on one molecule to show their proximity to the intersection of the channels. (b) Left: close-up view of b–c projection showing the position of the 2₁ screw-axis. Two molecules of 1 are shown. Right: Projection onto the a–b plane, with four molecules of 1 shown as well as the screw-axis symbol.

Figure 6. Distribution in ,ψ space for diffraction structures of molecules related to maltose. Points are labeled by their Refcodes from the Cambridge Crystal Structure Data Base (see Table 4 for translation of the Refcodes). The represents the conformation in 1. Linkage geometries from the FOXSUG20 structure are represented by , and those from the MAPNEW structure are indicated by . A dashed diagonal line separates the structures that form an O3–O2′ hydrogen bond from the structures that do not. The solid diagonal line represents polymeric structures having an h (advance per residue) of zero. Linkages above the line lead to right-handed helices, while those below lead to left-handed molecules.

Figure 7. Hybrid (see text) potential energy surfaces for maltose. The represents the linkage conformation observed in 1 and all other conformations from Figure 6 are shown by dots. (a) Dielectric constant set to 1.5. (b) Dielectric constant set to 3.5. (c) Dielectric constant set to 7.5. Contours above 20 kcal/mol are not shown; other contours (9, 11–14, 16–19) are omitted to avoid clutter.

Figure 8. An n–h map for amylose, showing the conformations for the various extrapolated amylose helices. The extrapolated n–h point for 1 is indicated by the . The vertical dashed line separates left- and right-handed structures. Structures with h = 0 or with n = 2 are neither right- nor left-handed.

Crystal data and structure refinement for maltose octapropanoate

Intermolecular dipole–dipole interactions (>0.12 kcal/mol) for an mm4-optimized model based on two methyl acetate molecules, numbered according to 1 (dielectric constant of 1.5)

Stacking distances for carbonyl groups in crystals and methyl acetate dimer models

Refcodes and chemical names for compounds related to maltose octapropanoate