Glyoxylic acid oxime

Hanessian reported the synthesis of enantiomerically pure or highly enriched allylglycine and its chain-substituted analogs from the reaction of the sultam derivatives of O-benzyl glyoxylic acid oxime with ally he bromides in the presence of zinc powder in aqueous ammonium chloride (Eq. 11.41).72 Brown noticed the critical importance of water in the asymmetric allylboration of /V-trimethylsilyIbcnzaldimines with B-allyldiisopinocampheylborane.73 The reaction required one equivalent of water to proceed (Eq. 11.42). 

The reaction can be applied to imines. Recently, the preparation of chiral allylglycines was effected by addition of allyl groups to the C=N bond in glyoxylic acid oximes modified as chiral sultams (Oppolzer chiral induction methodology).55 The yields (> 88%) and the diastereoselectivity (d.e. > 80 20) are excellent. 

Unsubstituted indoxazenes cannot be prepared in this way instead of the expected product one obtains the corresponding isomeric salicylonitrile (9) or its hydrolysis products.20 With o-bromophenyl-glyoxylic acid oxime (10) in alkaline solution the reaction proceeds similarly, with decarboxylation, ring opening, and hydrolysis to salicylic acid.21... 

Mercury fulminate also forms from malonic acid, mercury, and nitric acid. The first intermediate (hydroxyiminomalonic acid) forms by nitrosation of the starting malonic acid which then decarboxylates to glyoxylic acid oxime. The following reaction is analogous to the Wieland mechanism presented above [2, 16, 35, 88] ... 

The starting semicarbazones were most often prepared directly from the a-keto acids. Godfrin proceeded from a-alkyl acetoacetates, which were converted by oxidation with nitrosylsulfuric acid to a-keto-acid oximes and the latter transformed to semicarbazones or thioseraicarbazones by applying semicarbazide or thiosemicarbazide. For glyoxylic acid semicarbazone a very convenient procedure was employed, making use of the hydrolysis of nonisolated chloral semicarbazone. ... 

Addition to oxime ethers of glyoxylic acid generates A-benzyloxyamino acids. These reactions have been done in both organic solvents344 and aqueous mixtures.345 The reactions can be done with or without Bu3SnH as a chain carrier. 

The GC-MS methods described here reflect the practice in the laboratory of the author. Organic acids are extracted from biological fluids by liquid-liquid extraction after mixing the specimen with an internal standard solution and a small amount of mineral acid (HC1) to bring the pH to < 2. Oximation of 2-keto acids with hy-droxylamine hydrochloride is not performed routinely, but only as a repeat analysis when the primary analysis reveals an abnormal excretion of 2-keto acids (e.g., lactic acidemia, ketonuria) and the potential presence of other compounds (e.g., glyoxylic acid, succinylacetone). 

Oxime ethers derived from 2-pyridinecarboxaldehyde and glyoxylic acid can be allylated effectively in water with functionalized allylic bromides promoted by indium (Scheme 67). When the metal is positioned in close proximity to flanking heteroatomic centers, chelation by indium is operative and affects both reactivity and stereochemistry... 

The condensation of organolithium reagents (2 equiv.) with glyoxylate-derived oxime ethers (182) provides a direct method for the synthesis of a- -hydroxy amino acids (equation 22). Both glyoxylic acid and glyoxylamide oxime ethers are compatible with this process. A(>hydroxyaminoacetamides are also product in low/moderate yields by the addition of isonitriles to oximes (oxime ethers) analogous to the four component condensation described by Ugi. ... 

Thus, a new and convenient procedure has been developed by Defrancq and coworkers for the synthesis of 3 -ohgonucleotide conjugates 83 through the formation of glyoxyhc oxime bonds (Scheme 44). This has been achieved by using a novel sohd support 82 for ODN synthesis. Support 82 was conveniently prepared from a commercially available serine derivative in a few steps. The glyoxylic oxime bonds showed higher stability than aldoxime bonds at acidic to neutral pH but lower stabihty at alkaline pH. 

The tandem transesterification/[3 + 2]-cycloaddition methodology is be a powerful synthetic tool, since it guarantees high diastereoselectivity even under thermal conditions. It has been successfully apphed to synthetic work of the N-terminal amino acid component of Nikkomycin Bz (Scheme 11.53) (173). Thus, the sugar-based oxime is condensed with a glyoxylate hemiacetal to produce a chiral nitrone ester, which is then reacted with ( )-p-niethoxycinnamyl alcohol in the presence of a catalytic amount of TiCU at 100 °C. After the intramolecular cycloaddition, the... 

A potential method for the preparation of novel amino acids via the highly selective addition of radicals to the glyoxylic oxime derivative of Oppolzer s camphor sultam (88) has been reported.181 Both Lewis acid and non-Lewis acid-mediated reaction conditions for the addition of alkyl radicals generated from alkyl iodides and Et3B/Bu3SnH were examined. A new chiral auxiliary based upon (R,R)-2,5-diphenylpyiTolidine has been used in the addition of phenylthiyl radicals to unsaturated methacrylamides. The selectivity was found to be better than that reported for the structurally related 2,5-dimethylpyrrolidine derivative.182... 

A subsequent similar synthesis of a-amino acids was then reported by Naito et al. which used the indium-mediated alkylation and allyation reaction of the Oppolzer camphorsultam derivative of glyoxylic oxime ether <02CC1454>. 

The indium-mediated allylation of the Oppolzer camphorsultam derivatives of glyoxylic oxime ether proceeds with excellent diastereoselectivity in aqueous media, providing a variety of enantiomerically pure a-amino acids.269... 

Intramolecular asymmetric induction has also been used in electrochemistry as in the reduction of optically active alcohol esters or amides of a-keto [469,470] and unsaturated [471] acids and oximes [472] and in the oxidation of olefins [473]. A maximum asymmetric yield of 81% was obtained in the reduction of (5 )-4-isopropyl-2-oxazolidinone phenyl-glyoxylate [470]. Nonaka and coworkers [474,475] found that amino acid A-carboxy anhydrides were polymerized with various electrogenerated bases as catalyst to give the poly(amino acids) with high chirality in high yields. Conductive chiral poly(thiophenes) prepared by electropolymerization can be used for chiral anion recognition [476]. 

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... 

---