The Preferred Conformations of Glycosylalditols

Abstract

Crystal structure analysis shows 6-O-(ff-D-glucopyraiosyl)-D-glucitol (isomaltitol 1) to have a bent glucitol chain linked to glucose in normal 4Cl-chair form, the middle section forming a planar zigzag chain that extends into the pyranoid ring. Comparative assessment of the conformational features of 1, its D-tnannitOl analogue 2, and of some (1 4 4)-linked analogues allows -in combination with Jeffrey's alditol rules and the exo-anomeric effect principles -to predict with significant confidence the preferred conformations of glycosylalditols in general. Glycosylalditols, a sizable, long-known group of disaccharide-derived sugar alcohols'), have recently attracted considerable interest due to the high potential of isomaltitol [6-O-(cc-D-glucopyranosyl)-D-glucitol (l)] and its D-mannitol analogue 2 as non-cariogenic", l~w-nutritive~) sugar substitutes with about half the sweetness of sucrose4,'). The appeal inherent in such compounds raised questions as to structuresweetness relationships, which may be assessed in terms of the presently available, mostly contentious concepts after uncovering their conformational features. However, in contrast to the opulent con formational information on pyranoid sugars 7,8) and on acyclic sugar chains7x9), there appears to be an exceedingly scarce knowledge on systems, in which both of these structural features are combined. This is mainly due to highly complex NMR spectra of glycosylalditols -l3C-NMR and 270 MHz 'H-NMR spectra of 1 and 2, e.g., failed to provide any relevant conformational information") -thus necessitating crystal structure analyses, which in the case of (1 + 1)-or (1 + 6)-linked glycosylalditols have only been performed with 2"). Subject of this paper is the X-ray crystallographic determination of the conformation of 1 and a comparative assessment of the molecular geometries of 1 -4, as well as those of (1 -+ 4)-linked analogues, allowing elaboration of the principles that govern their basic conformational features. Bevorzugte Konformationen von Glycosylalditen

Sugar Alcohols

“…The crystal structure of 1,6-GPS is given in [237]. The melting range is 166-168 C and the specific rotation ½a 20 D ¼ þ92.…”

Some Disaccharide‐derived Building Blocks of Potential Industrial Utility

“…[87], in which the 3-OH of the reducing glucosyl residue remains free. The easily accessible 30 suggested oxidation to the respective 3-ulose, which is smoothly obtained on exposure to pyridinium chlorochromate as the oxidant; however, when subjecting 30 to oxidation with dimethyl sulfoxidelacetic anhydride, both is effected, oxidation of the 3-OH and p-elimination to provide the 0-glucosylated dihydropyranone 31 [88]:…”

“…and elimination either under reductive conditions (ZdHOAc) or by base. With lactose, for example, the respective hexa-0-acetyl-D-lactal(32) [ [94]. This quite versatile building block is a counterpart to the maltose-derived dihydropyranone 31, the difference being that the enolone structural element in the pyranoid ring is realized in the reverse arrangement.…”

Evolution of the Structural Representation of Sucrose [1]

“…Prod. 55 (1989 (U), crystallizes anhydrous and exhibits in its X-ray structure [71] (Fig. 10a) a linear extended-chain backbone running from C-2 of glucose to the penultimate 0-2, whereby the starch/st&lce 43 Nr.…”

“…Glucopyranosyl-a( 1+6)-sorbitol (GPS, 24): (a) X-ray structure[71] derived contact surface and molecular geometry for the solid state, the stick model insert clearly showing the kink of the terminal hydrophobicity profile in an orientation different from that in (a) to account for full visualization of hydrophobic (violet) and hydrophilic (red) regions.…”