L-Kynurenine

Fig. 10. Stmcture of daptomycin where L-Kyn is L-kynurenine and (h-threo) 3-MeGlu is L-// fi (9-3-methylglutamic acid.

Recently, two examples of the separation of enantiomers using CCC have been published (Fig. 1-2). The complete enantiomeric separation of commercial d,l-kynurenine (2) with bovine serum albumin (BSA) as a chiral selector in an aqueous-aqueous polymer phase system was achieved within 3.5 h [128]. Moreover, the chiral resolution of 100 mg of an estrogen receptor partial agonist (7-DMO, 3) was performed using a sulfated (3-cyclodextrin [129, 130], while previous attempts with unsubstituted cyclodextrin were not successful [124]. The same authors described the partial resolution of a glucose-6-phosphatase inhibitor (4) with a Whelk-0 derivative as chiral selector (5) [129]. 

Proteins (BSA or ovomucoid, OVM) have also been successful in the preparative resolution of enantiomers by liquid-liquid extraction, either between aqueous and lipophilic phases [181] or in aqueous two-phase systems (ATPS) [123, 180]. The resolution of d,l-kynurenine [180] and ofloxacin and carvediol [123] were performed using a countercurrent extraction process with eight separatory funnels. The significant number of stages needed for these complete resolutions in the mentioned references and others [123, 180, 189], can be overcome with more efficient techniques. Thus, the resolution of d,l-kynurenine performed by Sellergren et al. in 1988 by extraction experiments was improved with CCC technologies 10 years later [128]. 

Alkaloids derived from nicotinic acid contain a pyridine nucleus. Nicotinic acid itself is synthesized from L-tryptophan via A-formylkynurenine, L-kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic acid and quinolinic acid. 

One of the papiliochromes, papiliochrome II (142), isolated from Papilio butterflies, is actually a pair of optical isomers, papiliochromes Ila and lib. Compound 142 is hydrolyzed by treatment with 10 iV HCl to afford l-kynurenine and a new catecholamine (400) (71). Results of acid hydrolysis of the latter with 1 N HCl and the mass and C-NMR spectra suggest that the structure of 400 is iV-P-alanylnoradrenaline, which was proved by chemical synthesis. The C-NMR data indicate that papiliochrome II is represented as structure 142 in which the nitrogen of aromatic amino group of kynurenine is bonded to C-5 of the side chain ofiV-P-alanyldopamine. The existence of optical isomers, Ila and... 

Similar protocol has been successfully used for the preparation of / -aroylaminoacids (Equation (22)), including protected L-kynurenine. Careful exclusion of air is crucial for the success, as in the presence of oxygen, the formation of symmetrical ketone formed from organozinc reagent competes with carbonylative cross-coupling. ... 

The urine (20 ml) of anadromous, ovulated females was collected by catheterization. Repeated fractionation, guided by male behavioral response, over complementary chromatographic supports led to the isolation of a sufficient quantity of pure substance for full spectroscopic characterization. The active pheromonal compound was shown to be L-kynurenine (6). It was estimated to be present at a concentration of 1.1 mg 100 ml-1 of urine. Interestingly, that is a hundred or more times higher than the concentration in the ovulated female urine of rainbow or brown trout. The absolute configuration of 6 was determined by Marfey s analysis,40 which involves... 

L-Kynurenine (6) is a known oxidative metabolite of L-tryptophan. This study for the first time appears to represent this amino acid metabolite that has been identified as a pheromone in a vertebrate. Although additional minor constituents present in the active fraction were identified (.V-formylkynurenine, tyrosine, cystathionine, and prostaglandin F2a), none was observed to synergize the sex pheromonal activity of L-kynurenine (6). 

Tryptophan dioxygenase catalyzes the first step in the oxidative metabolism of L-tryptophan. L-Kynurenine is the product. 

L-Kynurenine was separated from 3-hydroxykynurenine (observed in some assays) by chromatography on a Beckman Ultrasphere ODS column (4.6 mm x 150 mm). The mobile phase (1.5 m/min) was a 5 235 mixture of acetonitrile and 0.1 M ammonium acetate buffer (pH 4.65). The column effluent was monitored at 365 nm. 

Tryptophan 2,3-dioxygenase catalyzes the conversion of L-tryptophan to N-formyl-L-kynurenine. The product is further converted, both spontaneously and enzymatically, to L-kynurenine. This assay measures both products. 

L-Kynurenine and /V-formyl-L-kynurenine are separated by chromatography on Perkin-Elmer CR Pecosphere column (4.6 mm x 30 mm, 3 /tm). The mobile phase contained 1 mAf phosphate buffer (pH 2.4) in 5% acetonitrile. The flow rate was 0.S mL/min, and 5 fiL was injected for analysis. Both compounds were detected at 234 nm and quantified by comparison with standard calibration curves. 

Kynureninase is involved in the oxidative metabolism of tryptophan. It catalyzes the conversion of L-kynurenine to anthranilic acid. The enzyme also converts L-3-hydroxykyneurenine to 3-hydroxyanthranilic acid. The latter compound has a high fluorescence, which is the basis for detection in this assay. 

Kynurenine 3-monoxygenase is present in the outer membrane of rat liver mitochondria, where it catalyzes the oxidation of L-kynurenine to 3-hydroxy-L-kynurenine. This assay follows the disappearance of the substrate, l-[G-3H]kynurenine. 

The diazo reaction, not given to kynurenine, is clearly produced by xanthurenic acid when present in urine. In view of this, Chiancone in 1935 administered 3 g L-tryptophan to a young man with bilateral tuberculosis and 1.5 g L-kynurenine to another young patient. By the methods ai ailable at that time, no xanthurenic acid was found in the urine of either individual (C4). 

Heath-Pagliuso S, Mui R, Milici A, Giese S, Chin R, Denison MS. 2000. Tryptophan metabolites, indole-3-pyrivic acid, DL-3-indolelactic acid, L-kynurenine and kynurenic acid activate Ah receptor signal transduction. Organohal. Compd. 49 289-92... 

Vorwerk CK, Kreutz MR, Dreyer EB, Sabel BA. 1996. Systemic L-kynurenine administration partially protects against NMDA, but not kainate-induced degeneration of retinal ganglion cells, and reduces visual discrimination deficits in adults rats. Invest Ophthalmol Vis Sci 37 2382-2392. 

Silver et al.58 have reported that during the active phase of EMS tryptophan metabolism via the kynurenine pathway was accentuated, probably secondary to induction of the enzyme indoleamine-2,3-dioxygenase. Indeed, patients with EMS generally have low plasma L-tryptophan and high plasma L-kynurenine and quinolinic acid levels. 

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