Tartronic dialdehyde

The hydroxylated compound thus formed would be hydroxymalonaldehyde —i.e. tartronic dialdehyde (8). This compound has never been obtained or studied, but its enol form, which is the so-called triose reductone (11) (14), is well known, and it is generally agreed that, in solution, the equilibrium... 

However, when we oxidized malonaldehyde (56) in the conditions just described for triose reductone, although formic acid and carbon dioxide were produced in high yields, the periodate consumption was erratic. Similar results were obtained with deoxy sugars. This discrepancy may be caused by the incomplete enolization of the first intermediate, hydroxy malonaldehyde —i.e. tartronic dialdehyde (5,22,32), to triose reductone, or may concern the hydroxylation step itself. 

As to the first point, tartronic dialdehyde (8) could, as has already been suggested (32), be oxidized by classical glycol cleavage to give three molar equivalents of formic acid (and no carbon dioxide) with the concomitant reduction of two (instead of three for the enol form) molar equivalents of periodate ... 

Crystalline triose reductone has been shown (56) by titration with strong base and with iodine, to exist in solution, for practical purposes, entirely as the enol form. In addition, the fact that it reduces exactly three molar equivalents of periodate to give quantitative yields of formic acid and of carbon dioxide indicates that it is also oxidized entirely in this form. However, nothing is known of the rate of enolization of tartronic dialdehyde and the possibility therefore remains that part of it may be oxidized in the dialdehydo form. If this were the case, the results of periodate oxidations would be dependent on the ratio of the rate of enolization of tartronic dialdehyde to the rate of its oxidation by periodate, since the oxidation of triose reductone is, again, for practical purposes, instantaneous. 

In explanation of this array of facts Fleury, Poirot and Fievet have offered the following mechanism. It is suggested that the meso-inositol molecule is initially attacked at two points with the formation of two moles of tartronic dialdehyde. This dialdehyde then rapidly rearranges HOH... 

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