Chemistry of Novel Compounds with Multifunctional Carbon Structure. 9. Molecular Design, Synthetic Studies, and NMR Investigation of Several Efficient Chiral Derivatizing Reagents which Give Very Large (19)F NMR Δδ Values in Enantiomeric Excess Determination

Article abstract of DOI:10.1021/jo00059a036

In order to develop efficient ee-determining reagents potentially superior to MTPA (1), some multifunctional compounds 2-5 were rationally designed.From NMR investigations of the analogous diastereomeric derivatives it was found that the chemical shift differences for each pair of diastereomers (Δδ values) for CFPA derivatives 5d-f were approximately five times greater in (19)F NMR spectra and two times greater in 1H NMR spectra than those of 1d-f.Synthesis of the optically pure CFPA, (-)-5a nd (+)-5a, was achieved by nitrosation of each diasteromer of the optically active N-(1-phenylethyl)amides, 5f_M and 5f_L, followed by thermal decomposition.Various derivatives were prepared by the condensation of 5b and 1b with alcohol and amine nucleophiles, and both Δδ_F and Δδ_H values were obtained for each compound.The CFPA derivatives 5d-m have proven to be significantly superior for ee determinations when compared to the corresponding MTPA derivatives 1d-m, particularly in compounds having remotely disposed chiral centers.