Glyoxylic acid. Table

In a detailed study on methylated permanganate-degradation products of aquatic humic and fulvic acids (originating from Black Lake, North Carolina, and Lake Drummont, Virginia) by means of gas chromatography/mass spectrometry, Liao et al. (1982) found methyl esters of benzenecarboxylic acids, furancarboxylic acids, aliphatic mono, di, and tribasic acids, and (car-boxyphenyl) glyoxylic acids (Table 3). The degradation products of fulvic and humic fractions from the two lakes were qualitatively similar, but dis-... 

For this purpose, recourse was made to allylic bromides that carry a stereocontrolling element of their own. The purpose was to elucidate the level and direction of the competitive involvement of intermolecular versus intramolecular modes of chelation when these options are allowed to vie for control of ic-facial stereoselectivity (75). The contrasting response of methyl 4-bromocrotonate and methyl (Z)-2-(bromomethyl)-2-butenoate to 2- and 3-pyridinecarboxaldehyde and to glyoxylic acid (Table IV) constitutes a useful reference standard. In this instance, a... 

Ito et al.40 examined the electrochemical reduction of C02 in dimethylsulfoxide (DMSO) with tetraalkylammonium salts at Pb, In, Zn, and Sn under high C02 pressures. At a Pb electrode, the main product was oxalic acid with additional products such as tartaric, malonic, glycolic, propionic, and n-butyric acids, while at In, Zn, and Sn electrodes, the yields of these products were very low (Table 3), and carbon monoxide was verified to be the main product even at a Pt electrode, CO was mainly produced in nonaqueous solvents such as acetonitrile and DMF.41 Also, the products in propylene carbonate42 were oxalic acid at Pb, CO at Sn and In, and substantial amounts of oxalic acid, glyoxylic acid, and CO at Zn, indicating again that the reduction products of C02 depend on the electrode materials used. 

Table 1. Results for the condensation between 2-alkoxyphenols and glyoxylic acid (GA) in aqueous sodium hydroxide. 

When conventional heating was used, a satisfactory yield was obtained after 4 h at 135 °C in a sealed tube [32]. Ethyl glyoxylate is a weaker carbonyl dienophile than diethyl mesoxalate, and a catalyst (ZnCl2) was added to afford the expected DA adducts with dienes 12 and 13 in goods yields (Table 9.2, entries 2 and 7). For reaction with 13, the catalyst SnCU [34] was substituted by ZnCl2 to prevent formation of the ene reaction product (Table 9.2, entry and 7). Although adduct 16 was previously prepared from 15 [32], its direct DA synthesis from 12 and glyoxylic acid could be performed under the action of MW and without a catalyst (Table 9.2, entry 3). 

The presence of furfural and hydroxymethyl-furfural, released from grapes affected by Botry-tis cinerea as well as from toasted oak in barrels (Table 13.20, Section 13.8.3), leads to the formation of orange-yellow and brick-red compounds. These xanthylium structures are formed by condensation of the aldehydes with catechin and anthocyanins (malvidin and cyanidin) (Es-Safi et al, 2000 and 2002). Oxidation of tartaric acid results in glyoxylic acid, which then... 

The hetero Diels-Alder reaction has also been carried out efficiently in water. For instance, glyoxylic acid undergoes cycloadditions with various dienes [20] although the carbonyl function is almost exclusively present as its hydrate form. Other pericyclic reactions such as 1,3 dipolar [21] or [4+3] cycloadditions [Eq. (1), Table 1], and Claisen rearrangement [22] gave better results when conducted in aqueous media than in organic solvents. 

Nineteen different compounds (or compound classes) that are known to be rapidly assimilated by bacterioplankton have been identified as DOM photoproducts (Table I). Five of these photoproducts are formed with source DOM from both freshwater and marine environments acetaldehyde, formaldehyde, glyoxylate, pyruvate, and amino acids. Nine others have been reported only from freshwater systems (acetate, butyrate, citrate, formate, levulinate, malonate, oxalate, succinate, and dissolved carbohydrates), whereas five have been reported only from marine systems (acetone, butanal,... 

Table 2.12 ont/ -Mannich-type reactions of aldehyde donors and N-PMP-protected glyoxylate imine catalyzed by (3/ ,5/ )-5-methyl-3-pyrrolidine-carboxylic acid (13) [73]. 

S)-Proline also catalyzed the Mannich-type reactions of unmodified aldehydes and N-PMP-protected imines to afford the corresponding enantiomerically enriched / -aminoaldehydes at 4 °C (Table 2.13) [71b]. The products were isolated after reduction with NaBH4, though oxidation to the / -amino acid is also possible. These reactions also provided the syn-isomer as the major diastereomer with high enantioselectivities, and proceeded well in other solvents (e.g., dioxane, THF, Et20). In the reaction of propionaldehyde and the N-PMP-imine of 4-nitrobenzaldehyde in DMF, the addition of water (up to 20%, v/v) did not affect the enantioselectivity. Similar results were obtained for the (S)-proline-catalyzed Mannich-type reactions with the glyoxylate imine where water did not reduce enantioselectivity [71b]. However, the enantioselectivity of the reaction of propionaldehyde and the N-PMP-imine of benzaldehyde in DMF was decreased by the addition of water or MeOH [71b]. 

Jang and co-workers reported on the development of an enantioselective radical addition reaction to glyoxylate oxime ether for the preparation of a-amino acids under mild reaction conditions with chiral quaternary ammonium salts of hypophosphorous acid in aqueous media.26 The newly prepared chiral quaternary ammonium hypophosphites are inexpensive, less toxic than metal-containing compounds and the reaction conditions and workup are mild and simple (Table 7.2). It is also important to note that chiral quaternary hypo-phosphites are recyclable without altering their performance. The... 

Diastereoselective radical additions to glyoxylic oxime ethers are well established however, only one recent report describes attempted enantioselective additions using chiral Lewis acids [26], It was found that bisoxazoline ligand 9 provided the best results as illustrated in Eq. (18) and Table 3. 

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