Optical purity determination, conformer populations and 1H NMR spectral simplification with lanthanide shift reagents--part IX. A method for improved analytical precision for "DOEt", 2,5-dimethoxy-4-ethylamphetamine.

The 60 MHz (1)H NMR spectra of the potent hallucinogen 2,5-dimethoxy-4-ethylamphetamine ("DOEt"), 1, have been studied in CDCl(3) at 28 degrees with the achiral shift reagent, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), 2, and the chiral reagents tris[3-(trifluoromethylhydroxymethylene)-d-camphorato] europium(III), 3, and tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato] europium(III), 4. Distinct enantiomeric shift differences, DeltaDeltadelta, were observed for the amphetamine CH(3) and the adjacent CH resonances using either 3 or 4 that permit direct optical purity determinations. A novel use of an external computing integrator as an accessory to a basic NMR is described; interfacing these instruments permits improved analytical precision for the reported optical purity determinations using nonracemic mixtures of known compositions. Relative abundances of the different conformers with respect to C(alpha)C(beta) bond rotation in the arylethylamine moiety is discussed based on coupling constants. Results are compared with the related hallucinogen, 3,4-methylenedioxyamphetamine.