Assignment of NMR spectral data of diastereomeric tetrahydrofuranyl acetals directly from their mixture by spectral simulation Scientific paper

Abstract

In this study, an NMR spectral analysis of the mixture of diastereo­meric acetals, synthesized from 2,3-dihydrofurane and a racemic mixture of cit­ronellol, was performed. ¹H-NMR full spin analysis was achieved by manually adjusting δ_H and J values (previously calculated using the Spartan software) to fit the experimentally available values, followed by further optimization using MestreNova software. The simulated ¹H- and ¹³C-NMR spectra of individual diastereomers, as well as their superimposed and summed spectra, were com­pared with the obtained experimental spectra. Spin simulation of proton signals was particularly useful for the assignment of the diastereotopic protons of tetra­hydrofuranyl moiety and diastereomer discrimination. The NMR spectral data of individual diastereomers – chemical shifts, coupling constants, HMBC and NOESY interactions were systematized in appropriate tables and schemes. To the best of our knowledge, this is for the first time that the complete assignment of tetra­hydrofuranyl moiety was performed, and the data obtained herein may be of great importance for the utilization of this protecting group in the future.