Homo- and Heteronuclear NMR Methods for Signal Assignments in 1H and 13C Spectra of 1-Aminoacyloxygermatran

Abstract

1-Aminoacyloxygermatran containing a hexacoordinated germanium atom and an amino acid substituent in its structure—L-valine—was synthesized and studied by high resolution ¹H and ¹³C NMR spectroscopy for the first time. Complete signal assignment in two different parts of ¹H spectra containing 8 and 12 overlapped multiplets from –O-CH₂- and –N-CH₂- protons was made by using homonuclear J-COSY, COSY and NOESY methods and on base data of heteronuclear HMQC and HMBC experiments. The spatial structure of the studied 1-aminoacyloxygermatran was proved on the basis of data on interproton through-space interactions obtained from the NOESY spectra at different mixing times from 0.3 to 1.2 s. Simultaneously, along with cross peaks from positive NOEs, exchange cross peaks between germinal protons of different -O-CH₂- groups were found in the same spectra, thus indicating the existence of a slow (in the NMR time scale) dynamic process in this compound associated with rearrangements within the atranium cycle.