Acyclic alditols

Alditols Acyclic Alditols Anhydro-Alditols Amino-Alditols... 

Like the polymethylene hydrocarbons, acyclic carbohydrates and alditols tend to adopt the planar, zigzag conformation wherein all of the carbon atoms lie in the same plane. " However, non-bonded interactions between parallel hydroxyl groups in the 1,3 positions (sy/i-axial interaction) are the most highly destabilizing, and, in xylitol and ribitol, this... 

Intramolecular cyclization can also be effected with acyclic intermediates derived from such readily available alditols as D-mannitol. Kuszmann and Vargha63 reported the formation of 2,5-anhydro-l,6-dibromo-l,6-dideoxy-4-0-(methylsulfonyl)-D-glucitol (63), in 73% yield, by boiling 3,5-di-0-acetyl-l,6-dibromo-l,6-dideoxy-2,4-di-0-... 

It so happens that the great majority of compounds separated as acetates are alditols or other polyhydric compounds, and this Section is therefore concerned with the problems of reduction and acetylation. There is no a priori reason why alditols and other polyols should not be separated as their trimethylsilyl ethers, and such methods are known (see Section VII,l,p. 57 Section XIII, p. 90 Table Va, p. 119 and Table Xlla, p. 151), but experience shows that the resolution of acyclic O-trimethylsilyl derivatives is less satisfactory than that of cyclic compounds. 

Appropriately substituted derivatives of acyclic sugars should behave in the same manner as the alditols. The only examples so far studied are239 2,3-di-0-tosyl-D,L-glycerose and its diethyl acetal, which react as follows ... 

Acyclic carbohydrate derivatives containing unsaturation, with some exceptions, exhibit much of the chemistry already described for cyclic analogues, and their usefulness should not be overlooked. Unsaturated derivatives of alditols can be made, for example, by standard eliminations from alditol v/r-disulfonates or epoxides or by /f-eliminations from O-substituted 1-deoxy-l-nitroalditols and 1-deoxy-l-sulfonylalditols. Additions of hydrogen and ammonia to the unsaturated nitroalditols made in this way offer, respectively, routes to 2-deoxy- and 2-amino-2-deoxyaldoses.255... 

In this Chapter, only anhydrides of aldoses and ketoses are included. Anhydrides of acyclic carbohydrates, for example, alditols, aldonic acids, and intermolecular anhydrides are not discussed. 

VIII. Unsatubated Acyclic Compounds 1. Alditol Derivatives... 

The relationship between configuration and conformation observed for the unsubstituted alditols in the crystalline state can be used to predict, with significant confidence, the favored conformations of other acyclic sugar derivatives whose structures have not yet been determined experimentally. 

For molecules in the solid state, it is possible that lattice forces may profoundly affect the process of adoption of a particular conformation, and thus the favored conformation of a molecule in the crystalline state is not necessarily the same as that adopted when the molecule is surrounded by a sheath of solvent molecules. Nevertheless, there is a high degree of correlation between the results of X-ray crystallography of alditols and their derivatives (see p. 69) and the conformations adopted by various types of acyclic sugar derivatives in solution. 

The action of hydrogen fluoride on acyclic alditol acetates gives deacetylation products and complex mixtures of isomers. This is understandable, because, in such flexible systems, it is possible for... 

Direct heteroarylation of the acyclic D-ribose derivative 226 with the maleimide phosphorus ylides 197 gave the corresponding 3-(alditol-l-ylidene)pyrroles 227 (69MI7) (Scheme 49). 

In acyclic alditols, a uzc-diol grouping consisting of secondary hydroxyl groups is usually oxidized more readily than one containing a primary and a... 

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