Hydroxycarboxylic acids alkoxycarboxylic acid

A more versatile behavior was observed with dianionic H(T 6H ligands (Table 9) diols act as bidentates,186,187 while cv-hydroxycarboxylic acids behave as monodentate monoanionic ligands, e.g. in cinnamates,188 or as bidentate dianionic ligands189,190 in alkoxycarboxylates. In the case of catechol, ionic species were shown to exist in solution for both metals, but were isolated for tantalum only.191 The bidentate monoanionic diphenylphosphinate ligand can replace from one to three alkoxo groups in Ta(OMe)5 to yield low molecular weight polymers (Table 9).192... 

Combination of the coordinating ability of metal ions for hydroxy group containing compounds with the before mentioned exceptional behaviours of DBTA in chiral recognation processes gave us a new possibility for direct resolution of a-alkoxycarboxylic acids, a-hydroxycarboxylic acid esters and series of racemic alcohols... 

Crowded structure of these diastereoisomers limitate the scope of this resolution method to relatively small racemic a-alkoxycarboxylic acids. Furthermore, the presence of an alkoxy group in the racemate seems to be essential because its oxygen atom also coordinates to the calcium ion. Luck of such coordination hindered formation of crystalline complex when a-chlorocarboxylic acids were tested. On the other hand, a-hydroxycarboxylic acids precipitated from the reaction mixture as simple calcium salts because of their lowest solubility among the possible combinations of the components of the reaction mixtures. 

Dialkylborinyl triflateslethyldiisopropylamine Stereospecific aldol-type condensation with a-alkoxycarboxylic acid esters under mild conditions 5> /f-a-Alkoxy-p-hydroxycarboxylic acid esters... 

Hydroxycarboxylic acids from alkoxycarboxylic acid amides with preceding reduction of nitro compounds to amines s. 17, 18... 

Alkoxycarboxylic acids from hydroxycarboxylic acid esters via alkoxy-carboxylic acid esters—a,hydroxyl groups of aminophenols s. 11, 41... 

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