TOWARD SOLUTION-STATE STRUCTURE - A LI-6,H-1 HOESY NMR, X-RAY-DIFFRACTION, SEMIEMPIRICAL (PM3, MNDO), AND AB-INITIO COMPUTATIONAL STUDY OF A CHIRAL LITHIUM AMIDE

Computational studies of a chiral lithium amide (lithium ethoxy-(R)-1- phenylethyl)((S)-1-phenylethyl)amide, 3) using the solid-state structu re as a reference geometry showed that there were only small differenc es between the X-ray and ab initio and PM3 calculated structures. Furt hermore, we have shown that reference distances from either X-ray or a b initio/PM3 can be used for the calculation of Li-H distances using L i-H NOE data. The calculations of Li-H distances using HOESY buildup r ates showed that the solution structure of 3 THF is similar to the str ucture obtained in the gas phase (calculated) and in the solid phase ( X-ray). Small variations of +/-0.2 Angstrom were observed between X-ra y/ab initio and NOE data for distances less than 4 Angstrom.