Glyoxylic acid esters

Imines derived from aniline and glyoxylic acid esters can be regarded as electron-poor 2-azadienes, in which an aromatic carbon—carbon double bond takes part of the diene system. In this context, Prato and Scorrano et al. were able to achieve the [4 + 2] cycloaddition of ethyl N-phenyl glyoxylate imines with dihydrofuran and indene leading to hexahydrof-uro[3,2-c]- and tetrahydro-7//-indeno[2,l-c]quinolines, respectively, in moderate to good yields (88JHC1831). Similarly, tetrahydroquinoline derivatives were formed by [4 + 2] cycloaddition of 1,2-bis(trimethylsily-... 

Access to racemic thiazolidine-2-carboxylic acid (3-thiaproline, 12) is obtained by reacting cysteamine (49) with glyoxylic acid ester (Scheme 9), 165>182>1831 whilst the reaction of (R)-cysteine with glyoxylic acid 184 1851 leads to (2/ /S,5/ )-thiazolidine-2-carboxylic acid. 185 The diastereomers of thiazolidine-2-carboxylic add (12) are rapidly interconverting and therefore cannot be separated. 185 In the presence of (2R,3R)- and (2S,3S)-tartaric acid, reaction of cysteamine with glyoxylic acid leads to the enantiomerically pure (2/ )- and (2S)-thia-zolidine-2-carboxylic acid salts. 186 The acids undergo fast racemization in acetic acid. 186 ... 

Recently, Sprinson and Chargaff97 have inferred that periodate oxidation of L-sorbose gives rise to two esters of glycolaldehyde, namely the glyoxylic acid ester (XLII) and probably the glycolic acid ester (XLIII). 

D-Sacfharic acid 3,6-monolactone Glyoxylic acid ester of — 67... 

In the course of the synthesis, the mixture of benzylated cycloadduct 257, obtained from diene 255 and glyoxylic acid ester 256, was hydroxylated with osmium tetraoxide to afford mixture of unseparable diols 258 (hydroxyalation onto si face of the si cycloadducts) and 259 (hydroxyalation onto re face of the re cycloadducts). This mixture... 

Asym. ene synthesis with glyoxylic acid esters... 

An improved method has been described for the preparation of glyoxylic acid esters by oxidative cleavage of the corresponding tartrates use of ethereal periodic acid necessitates no work-up procedure, obviating the problem of water solubility of the lower glyoxylates. j8-Keto-csters are dehy ated to the corresponding acetylenic esters by oxidation of the derived 5-pyrazolones with thallium(in) nitrate (Scheme 36). 

In summary, the title compound, readily available from diethyl oxalate, is a synthetically useful synthon in various C-C bondforming reactions, requiring only catalytic amounts of mild Lewis acids such as zinc chloride. Mtematives to such an acyl anion equivalent include dithiane derivatives of glyoxylic acid esters, which have not been tested as widely and which require some synthetic effort in the final deprotection step. ... 

Aminals and hemiaminals of glyoxylic acid esters were employed in Diels-Alder-reactions with cyclohexa-1,3-diene (491, 492), the intermediate imino acid derivative acting as dienophile. Several authors dealt with asymmetric hydrogenation of optically active Schiff bases of a-keto acids (532—535). For prior publications in this field these papers should be consulted. 

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