Sugars acid cleavage

T. Trnka and M. Cerny, Syntheses with anhydro sugars. 10. Cleavage of the oxirane ring in 1,6 2,3- and l,6 3,4-dianhydro-/i-i)-hexopyranoses with potassium hydroxide and sulfuric acid, Collect. Czech. Chem. Commun., 36 (1971) 2216-2225. 

Diols (glycols), such as those formed by dihydroxylation of alkenes, are cleaved by periodic acid (HI04). The products are the same ketones and aldehydes that would be formed by ozonolysis-reduction of the alkene. Dihydroxylation followed by periodic acid cleavage serves as a useful alternative to ozonolysis, and the periodate cleavage by itself is useful for determining the structures of sugars (Chapter 23). 

Determination of Ring Size Periodic Acid Cleavage of Sugars... 

Within experimental limits, leaves labeled with l-[5- C]- or l-[6- C]ascorbic acid gave comparable results (Table III). Additively, the C in CO2, sugars, and malic acid accounted to 62-63% of that present in the leaves. Another 7% appeared in the residue as glycans. The total amount of C found in hexose or products of hexose metabolism of l-[5- C]- or L-[6- C]ascorbic acid labeled leaves was similar to that found in tartrate (and CO2) after labeling with l-[1- C]- or l-[4- C]-ascorbic acid. Cleavage of the carbon chain of ascorbic acid at the C4-C5 bond accounts for these observations. 

The hydrolysis of glycose diethyl dithioacetals and 1-thioglycosides in the presence of mercuric chloride represents a special case where the high afl nity of mercury for the sulfur function profoundly influences the reaction. The procedure has been used as an alternative to acid hydrolysis for conversion of a 1-thiofuranoside into the free sugar without cleavage of an acid-labile group, as in the one-step conversion of ethyl 2-acetamido-2-deoxy-l-thio-o-D-xylofuranoside into 2-acetamido-2-deoxy-D-xylose. Attempted replacement of the ethylthio group by methoxyl in ethyl 1-thio-/3-D-mannopyranoside, with mercuric chloride and cadmium carbonate in methanol, was unsuccessful. Mercuric chloride normally effects desulfurization of acyclic dithioacetals. ... 

Eeton-saure, /. ketonic acid, keto acid, -spal-tung,/. ketonic cleavage, -zucker, m. ketonic sugar. 

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