Thiols reaction with aldoses

Osmium tetroxide, reaction with alkenes, 235-236 toxicity of, 235 Oxalic add, structure of, 753 Oxaloacetic acid, structure of, 753 Oxetane, reaction with Grignard reagents, 680 Oxidation, 233, 348 alcohols, 623-626 aldehydes, 700-701 aldoses, 992-994 alkenes, 233-236 biological, 625-626 phenols, 631 sulfides, 670 thiols, 668... 

From Acylated Aldoses by Reaction with a Thiol in the Presence of Lewis Acid. 181... 

In their reaction with alcohols under acid catalysis, the aldoses differ from the simple, or unhydroxylated, aldehydes in forming mixed monocylic acetals (glycosides) rather than acyclic dialkyl acetals. However, Fischer 138) found that, on shaking a cold solution of an aldose in concentrated hydrochloric acid with a thiol, a crystalline product separated which was the dithioacetal (mercaptal) of the acyclic structure. These substances have... 

Carbonyl functions often are protected as thioacetals, because these derivatives are stable to acids and bases. Dithio-acetals and -ketals generally are prepared by reaction of the carbonyl compound with a thiol in the presence of an acid catalyst. This transformation has been used in carbohydrate chemistry for a long time to lock aldoses in their acyclic forms (see equation 26). In recent years, this blocking principle for carbohydrates has been exploited in several chiral pool syntheses. Several other methods for... 

Fischer420 reported the preparation of mercaptals from carbohydrates the reaction can be applied to all aldoses and aliphatic thiols, but fails with thio-phenols and also with fructose and sorbose,421 so that it can be used to separate, e.g., glucose from a mixture with fructose and sorbose. 

Hara et al. [117] demonstrated an excellent separation of the enantiomers of nine aldoses by GC as their diastereomeric thiazolidine derivatives. The sugars were derivatized with L-cysteine methyl ester (49) and subsequently silylated. This simple derivatization, including the acylation, was carried out in pyridine at 60 C. The rapid reaction of thiols with the carbonyl group of sugars was also exploited by Little [118], who used (-k)-l-phenylethanethiol (50) to form acyclic dithioacetals. 

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