Hydroxyl groups sodium periodate

This same type of modification strategy also can be used to create highly reactive groups from functionalities of rather low reactivity. For instance, carbohydrate chains on glycoproteins can be modified with sodium periodate to transform their rather unreactive hydroxyl groups into highly reactive aldehydes. Similarly, cystine or disulfide residues in proteins can be selectively reduced to form active sulfhydryls, or 5 -phosphate groups of DNA can be transformed to yield modifiable amines. 

The carbonyl-reactive group on these crosslinkers is a hydrazide that can form hydrazone bonds with aldehyde residues. To utilize this functional group with carbohydrate-containing molecules, the sugars first must be mildly oxidized to contain aldehyde groups by treatment with sodium periodate. Oxidation with this compound will cleave adjacent carbon-carbon bonds which possess hydroxyl groups, as are abundant in polysaccharide molecules (Chapter 1, Sections 2 and 4.4). 

Molecules containing polysaccharide chains may be oxidized to possess reactive aldehyde residues by treatment with sodium periodate. Any adjacent carbon atoms containing hydroxyl groups will be affected, cleaving the carbon-carbon bond and transforming the hydroxyls into... 

Hall and Bischofberger177 found that, when 2,3 5,6-di-0-isopro-pylidene-D-gulono-1,4-lactone was oxidized with ruthenium(VIII) oxide and an excess of sodium periodate, it gave 2,3 5,6-di-0-isopro-pylidene-D-riho-4-hexulosono-l,4-[(R) or (S)]-lactol. Similar results were observed with 2,3 5,6-di-0-isopropylidene-D-mannono-1,4-lactone and 2,3 5,6-di-O-isopropylidene-D-allono-l,4-lactone. This oxidation presumably proceeds by way of lactone cleavage and oxidation of the free 4-hydroxyl group followed, on acidification by relac-tonization, and formation of the new lactol. 

C]gulono- 1,4-lactone. The hydroxyl groups at C-2 and -3 were protected by isopropylidenation, and the 5,6-glycol was oxidized by sodium periodate. Treatment of the resulting syrupy product with methanolic hydrogen chloride, followed by borohydride reduction and hydrolysis, afforded L-[5-,4C]arabinose. 

The oxidation may be performed at pH 5.0 by addition of an aqueous solution of sodium metaperiodate. The reaction is allowed to proceed in the dark at 4 °C and after 24 hours the excess periodate is destroyed by the addition of ethylene glycol. The aims in periodate oxidation are to elucidate the number of neighbouring hydroxyl groups by estimating the number of moles of periodate consumed and to determine the structure of the moiety remaining after the reaction. The amount of periodate used in the reaction may be determined in several ways, including titrimetric and spectrophotometric methods. 

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