Alditols configuration

The reaction is used for the chain extension of aldoses in the synthesis of new or unusual sugars In this case the starting material l arabinose is an abundant natural product and possesses the correct configurations at its three chirality centers for elaboration to the relatively rare l enantiomers of glucose and mannose After cyanohydrin formation the cyano groups are converted to aldehyde functions by hydrogenation m aqueous solution Under these conditions —C=N is reduced to —CH=NH and hydrolyzes rapidly to —CH=0 Use of a poisoned palladium on barium sulfate catalyst prevents further reduction to the alditols... 

In the course of their studies of pseudouridine,164 Asbun and S. B. Binkley183 reported the synthesis of 5-/3-D-arabinofuranosyl- and 5-/3-D-xylofuranosyl-uracil (258 and 259) by the acid-catalyzed ring-closure of the corresponding alditol derivatives. The configuration at the anomeric carbon atom was determined on the basis of optical rotatory dispersion studies. 

This enzyme [EC 1.1.1.16] catalyzes the reaction of galac-titol with NAD to produce o-tagatose and NADH. The enzyme will also catalyze the conversion of other alditols containing an T-threo configuration adjacent to a primary alcohol group. 

Defaye19 called attention to the fact that the 2,5-anhydro-tri-0-(p-nitrobenzoyl)-D-lyxitol that he prepared is the enantiomorph of Barker and Fletcher s 1,4-anhydro-tri-0-(p-nitrobenzoyl)-L-arabinitol.l4alditol anhydrides derived, without Walden inversion, from two configurationally different sugars have been shown experimentally to possess the same, although enantiomorphic, configuration. 

Problem 22.8 Glucose is reduced to a single alditol fructose is reduced to two epimers, one of which is identical to the alditol from glucose. Explain in terms of configurations. ... 

The chiral C, C, and C (see Problem 22.5(u)] of glucose and fructose have the same configuration. The identical alditols also have the same configuration at C . 

Consideration of rotatory powers of l,l-bis(acylamido)-l-deoxy-alditols showed79 certain correlations between optical rotation (d line of sodium) and configuration that can be summarized as follows. (a) When the acyl group is aliphatic (for example, acetyl or propionyl), the alditol will be dextrorotatory in water if the configuration of C-2 is S. (The rule does not apply to peracetylated derivatives.) (b) When the two substituents on C-l are benzamido and the configuration at C-2 is S, a solution of the alditol in pyridine will be levorotatory. Peracetylation does not alter applicability of this rule, (c) The abso-... 

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