Biomimetic transamination

A related synthetic approach involves the biomimetic transamination of a-keto acids with chiral pyridoxamine analogs (eq 7) or achiral pyridoxamine analogs in the pres-... 

Wu P, Brand L. N-terminal modification of proteins for fluorescence measurements. Methods Enzymol. 1997 278 321-330. Gilmore JM, Scheck RA, Esser-Kahn AP, Joshi NS, Erancis MB. N-terminal protein modification through a biomimetic transamination reaction. Angew. Chem. Int. Ed. 2006 45 5307-5311. Christman KL, Broyer RM, Tolstyka ZP, Maynard HD. Site-specific protein immobilization through N-terminal oxime linkages. J. Mater. Chem. 2007 17 2021-2027. 

Soloshonok, V. A. and Kuklar, V. P. (1997) Biomimetic transamination of a-keto perfluoro-carboxylic esters. An efficient preparative synthesis of P,p,P-trifluoroalanine. Tetrahedron, 53, 8307-8314. 

Hjehnencrantz, A. and Berg, U. (2002) New approach to biomimetic transamination using bifunctional [l,3]-proton transfer catalysis in thioxanthenyl dioxide imines. The Journal of Organic Chemistry, 67, 3585-3594. 

Furthermore, oxime formation has been used to funetionalize proteins for example, N-terminal oxidation of interleukin 8 with sodium periodate and biomimetic transamination of myoglobin with pyridoxal-5-phosphate, followed by site-specific protein EGylation with hydrojgrlamine-functionalized polymer blocks. The selectivity of this reaction is limited by the fact that other amino acids within the protein ean be oxidized as well, and incomplete and unselective transamination can take plaee. ... 

Soloshonok, V.A., Catt, H.T., and Ono, T. (2009) Continuous-flow asymmetric biomimetic transamination. 

Soloshonok and co-workers have developed a method for the synthesis of a-(perfluoro-alkyl)amines from perfluoroalkyl carbonyl compounds by a transamination involving an azomethine a/omethine (Schiffbase) isomerization. They call this method a biomimetic, base-catalyzed 1,3-proton shift reaction, and have applied it to perfluoroaldehydes,12-15 perfluoroalkyl ketones,12 18 / -(perfluoroalkyl)-/l-oxo esters,15 16 19 24 and - -( perfluoroalkyl)-a-oxo es-ters2 " -26 to synthesize the corresponding a-(perfluoroalkyl)amincs, / -(perfluoroalkyl )-/i-amino acids, and 3 -(perfluoroalkyl)- x-amino acids. 

Different molecular mechanisms have been separately postulated for dibromo-phakellin [74], dibromoagelaspongin [91], agelastatin [92], mauritiamine [88], and palau amine [78]. A1 Mourabit and Potier proposed a universal chemical pathway, starting from the simple precursors 101 and 140 and leading to over 60 pyrrole-imidazole alkaloids [80]. A new biomimetic spontaneous conversion of proline to 2-aminoimidazolinone derivatives using a self-catalyzed intramolecular transamination reaction together with peroxide dismutation as key step has been described [166]. This work has pointed to dispacamide A as the forerunner of oroidin and compounds 101 and 140 as probable hydrolysis products of oroidin and not the precursors. In this... 

The transformations themselves involved reactions of ketoacids with a pyridoxamine unit, either covalently attached to the polymer or reversibly bound to the hydrophobic core (29), which converted the ketoacids to amino acids, and the pyridoxamine was converted to a pyridoxal unit either covalently attached to the polymer or reversibly dissociated from the polymer. This reaction was modeled directly on the transamination process observed in natural enzymes. However, the second part of a full transamination in nature is the reaction of the pyridoxal with a different amino acid, which runs the transamination backward to form the pyridoxamine again while converting the new amino acid into its corresponding ketoacid. We found that such a process was too slow in our biomimetic system and could not compete with the rapid aldol condensation of the ketoacids with the pyridoxal. 

Fig. 10.3-13 A biomimetic strategy for transamination at pH 6.5 and at 22-37 °C. N-terminal modification. After condensation The resulting pyruvamides can be further with pyridoxal phosphate (PLP), a variety of derivatized through oxime formation. N-terminal amino acids undergo oxidative...

The group of Gong and coworkers explored a biomimetic 1,3-dipolar cycloaddition between a-ketoester 79 and benzylamine derivatives 80 with electron-deficient olefins 81a,b to devise a straightforward route to proline derivatives 82 in high yields and enantioselectivities [49]. The proposed biomimetic three-component 1,3-dipolar cycloaddition proceeds as illustrated in Scheme 2.22a. The azomethine ylide B is formed, via a transamination from ketimine ester A, which is in turn prepared from a-ketoesters 79 and benzyl-amine derivatives 80 then, the 1,3-dipolar cycloaddition with electron-poor olefins 81a takes place. For this purpose, the bisphosphoric acid 83 was found to be the catalyst of choice to promote such transformation (Scheme 2.22b). Replacing dimethyl maleate (previously used as deficient olefins) by methyleneindolinones, the same approach could be extended to spirooxindoles synthesis in high yields and... 

Transamination On-column 1,3-proton shift reactions-a key transformation in the biomimetic reductive amination process - were investigated using simple silica-adsorbed l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) catalyst [42, 43]. This process enabled chirality transfer from (H)-l-phenylethylamine to perfluoroalky-lated ketones. The continuous-flow process proved to be far superior to the batch processes, both from an economical and synthetic point of view. 

Catalytic asymmetric transamination of i-keto carboxylic esters 94 catalyzed by a chiral base was firstly reported by Soloshonosk et al. [40a] providing an original biomimetic approach to p-fluoroalkyl- 3-amino acids. This transformation involves the formation of A-benzyl enamines 96 in tautomeric equilibrium with A-benzyl... 

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