Galactaric acid lactone

The reaction probably proceeds via the cyclic forms of the sugars and lactones, as equilibria between the various cyclic forms and the acyclic form are presumably established rapidly under the strongly acidic conditions of these oxidations. Thus, D-galactose undergoes oxidation to (acyclic) galactaric acid, whereas similar reaction of D-mannose affords a dilactone (see preceding Chapter). 

Dimerization of 2-amino-3,4,6-tri-0-benzyl-2-deoxy-D-glucose with l.l -thionyl-or sulfonyl-di-imidazole gave the fructosazine and bis-tetrahydropyrano-piper-azine derivatives 73 and 74 in a ratio of 1 5, respectively a related compound appeared in Vol. 25, p.l32. The P-carboline derivative 75, isolated as a natural product from a hybrid plant cell culture product, was synthesized in six steps from tryptamine and ( )-4,5,6-tri-0-acetyl-2,3-dideoxy-D-ery/Aro-hex-2-enose. Thiazolo-triazoles such as 76, termed acyclo-C-nucleosides, were obtained on deacetylation of the product from condensation of peracetylated D-gluconic or galactaric acids with 4-araino-3-aryl-l,2,4-triazole-5-thiols in the presence of POCls. The related 1,2,4-triazole 77 and dihydroimidazole 78 were obtained by condensation of D-glucono-1,5-lactone with aminoguanidine and ethylenedia-mine, respectively, followed by acetylation then O-deacetylation. ... 

Methyl ester Methyl galactoside Methyl galactoside-methyl ester Methyl galactoside-lactone Galactaric acid... 

Typically, condensations to polyamide (II), are carried out between an activated, i.e., esterified (diester, ester/lactone, dilactone) form of the aldaric acid (I), and a primary diamine in a polar protic solvent such as methanol at room temperature. Under those conditions any starting single ester form of a five or six carbon aldaric acid is rapidly converted to an equilibrium mixture of acyclic diester and ester/lactone forms. Dilactone, if formed at all, is present in only small amounts. The starting monomer esterified form(s) of the aldaric acid differ from one acid to an other. For example, the monomers of choice for L-tartaric acid (1) and weso-galactaric acid (4) are simple diesters, while for D-glucaric acid suitable monomers are ester/lactones, dilactone, or even the entire alcohol esterified mixture (10). Xylaric acid is also conveniently polymerized as its esterification mixture while the D-mannaric acid monomer is the 1,4 6,3-dilactone (13a). 

The aqueous-bromine oxidation rate was determined for a number of other anomeric pairs of aldoses and it was found that, in general, the jS forms (see page 17) react faster. This phenomenon has also been observed for a-D- and /S-D-galactopyraniironic acid oxidation of these compounds provides a mixture of optically active lactones of galactaric (mucic) acid. This constitutes interesting evidence for the direct oxidation of the cyclic modifications (pyranose and furanose forms), since the oxidation of... 

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