Fluoroimines from the reaction of fluoro amino acids or fluoroketo acids with the aldehyde or amine form of vitamin B6: 2—Stereochemical aspects of their formation from β-fluoroaspartates or β-fluorooxaloacetate, using19F NMR
作者:M. C. Salon、S. Hamman、C. G. Beguin
DOI:10.1002/omr.1270210409
日期:1983.4
AbstractThe fluorine NMR spectra of systems initially containing 0.05–0.1 M of pyridoxal 5′‐phosphate and erythro‐β‐fluoroaspartate (or threo‐β‐fluoroaspartate) in D2O solution were examined over the pD range 1–12. The formation of the aldimine Schiff base gave only one stereoisomer, whcih was trapped with sodium borohydride. Reactions of pyriodoxamine 5′‐phosphate and fluorooxaloacetate were examined under the same conditions. A mixture of two products was given, identified as two ketimine Schiff bases (E and Z isomers) with well characterized fluorine chemical shifts and 2J(DF) values. This mixture, trapped with sodium borohydride, gives the two reduced erythro and threo aldimines. The configurations and conformations of all reaction products were determined using the 3J(HF) values and their correlation with the fluorine chemical shift. The role of the 3‐phenolate oxygen of the pyridine ring, of the conjugate acid of the iminium nitrogen and of the carboxylate oxygen in ionic or hydrogen bond interactions in the determination of the stereochemistry is discussed.
Fluoroimines from the reaction of fluoroamino acids or fluoroketo acids with the aldehyde or amine form of vitamin B6: Part III. Influence of fluorine on the formation and the reactivity of fluoroimines derived from β-fluoroaspartates or β-fluorooxaloacetate
作者:M.C. Salon、S. Hamman、C.G. Beguin
DOI:10.1016/s0022-1139(00)80907-0
日期:1985.4
in oxaloacetate, the typical amino acid-keto acid couple in transamination, induces large effects in their reaction with respectively pyridoxal 5′-phosphate (PLP) (1) and pyridoxamine 5′-phosphate (PMP) (4). The formation of imine intermediates through reaction of 1 with erythro or threo-β-fluoroaspartate (2e and 2t) and through reaction of 4 with β-fluorooxaloacetate 5 is highly favored in comparison