Nonoxidative hydroxy

A pure culture of the organism was inoculated into a basal medium with the addition of 0.025% caffeic acid. After 7 days incubation at 25°C under conditions of reduced oxygen tension, the caffeic acid was completely metabolized. Metabolites of caffeic acid are identified as dihydrocaffeic acid and ethyl catechol, respectively. In the 1960s, it has been reported that a constitutive enzyme present in strains of Aerobacter decarboxylates caffeic acid to 4-vinylcatechol nonoxidatively [20], Several cinnamic acids have been tested and the decarboxylation product from /7-coumaric acid has been identified as 4-vinylphenol. Thus, the bacterial enzyme activity requires a relatively unhindered 4-hydroxy group on the aromatic ring and an acrylic acid side chain. 

The a-keto acid decarboxylases such as pyruvate (E.C. 4.1.1.1) and benzoyl formate (E.C. 4.1.1.7) decarboxylases are a thiamine pyrophosphate (TPP)-dependent group of enzymes, which in addition to nonoxidatively decarboxylating their substrates, catalyze a carboligation reaction forming a C-C bond leading to the formation of a-hydroxy ketones.269-270 The hydroxy ketone (R)-phenylacetylcarbinol (55), a precursor to L-ephedrine (56), has been synthesized with pyruvate decarboxylase (Scheme 19.35). BASF scientists have made mutations in the pyruvate decarboxylase from Zymomonas mobilis to make the enzyme more resistant than the wild-type enzyme to inactivation by acetaldehyde for the preparation of chiral phenylacetylcarbinols.271... 

METHYL-2-HYDROXY-ETHYLAMINE (78-91-1) Combustible liquid (flash point 145°F/63°C). Violent reaction with strong oxidizers, strong acids, isopropyl percarbonate, ni-trosyl perchlorate. Incompatible with aldehydes, nonoxidizing mineral acids, cellulose nitrate (of high surface area), cresols, isocyanates, nitrates, nitric acid, organic anhydrides, phenols, sulfuric acid. Attacks aluminum, copper, zinc, or their alloys and galvanized steel. 

Prior to Davis and co-workers introduction of trans-( )-2-(phenylsulfonyl)-3-phenyloxaziridine (1) for direct enolate oxidation in 1984, there were several nonoxidative procedures for the formation of optically active a-hydroxy carbonyl compounds, but only one actively practiced oxidative method for the synthesis of such compounds.2... 

Br, or I) (equation 1). Another method relies on alkylation of a-hydroxy or a-alkoxy carbonyl compounds. The induction of diastereoselectivty, in these cases, is achieved through the use of chiral auxiliaries and other stereodirecting groups (equation 2). The third method frequently utilizes the nucleophilic addition of hydride or other carbanions to a-dicarbonyl compounds (equation 3). In addition to being laborious, nonoxidative methods are limited to the synthesis of acyclic compounds, which greatly reduces the magnitude of their synthetic practicality. 

The aromatic amino acid L-phenylalanine (primary metabolite) is directed into the phe-nylpropanoid pathway leading to hydroxy-cinnamic acids, lignin and flavonoids by the activity of L-phenylalanine ammonia-lyase (PAL), which brings about its nonoxidative deamination yielding ammonia and tvans-cinnamic acid (Fig. 1). PAL is one of the most studied plant enzymes, and its crystal structure has recently been solved [2]. PAL is related to the histidine and tyrosine ammonia-lyases of amino acid catabolism. A class of bifunctional PALs found in monocotyle-donous plants and yeast can also deaminate tyrosine [3]. A single His residue is responsible for this switch in substrate preference [3, 4]. All three enzymes share a unique MIO (4-methylidene-imidazole-5-one) prosthetic group at the active site. This is formed auto-catalytically from the tripeptide Ala-Ser-Gly by cyclization and dehydration during a late... 

Yoshioka, T., T. Suzuki and T. Uematsu. 1989. Biotransformation of N-substituted aromatic compounds in mammalian spermatozoa. Nonoxidative formation of N-hydroxy-N-arylacetamides from nitroso aromatic compounds. J. Biol. Chem. 264 12432-12438. 

Pyruvate decarboxylase is able to catalyze two different reactions the nonoxidative decarboxylation of a-keto acids to the corresponding aldehydes [10,15-17] and a car-boxyligase side reaction leading to the formation of hydroxy ketones [18,19]. An understanding of why the last reaction is catalyzed by pyruvate decarboxylase, the physiological role of which is to decarboxylate pyruvate to acetaldehyde, was revealed by the discovery that pyruvate decarboxylase is homologous with acetolactate synthase [20], the enzyme catalyzing an acyloin condensation in the first step of isoleucine-valine biosynthesis. 

---