D iCE: Diastereomeric in Silico Chiral Elucidation, Expanded DP4 Probability Theory Method for Diastereomer and Structural Assignment

Abstract

NMR chemical shift prediction at the B3LYP/cc-pVDZ level of theory was used to develop a highly accurate probability theory algorithm for the determination of the stereochemistry of diastereomers as well as the regiochemistry. DFT-GIAO calculations were performed for each conformer using geometry optimization and a CPCM solvent model. Boltzmann averaged shielding constants were converted to chemical shifts for ¹H and ¹³C, using the generalized linear scaling terms determined in four different solvents for ¹H and ¹³C and extended to ¹⁵N in DMSO. The probability theory algorithm, D iCE, was based on the DP4 method and developed for ¹H, ¹³C, and ¹⁵N NMR using individual and combined probability data. The chemical shift calculation errors were fitted to a Student's t-distribution for ¹H and ¹³C and a normal distribution for ¹⁵N. The application yielded a high accuracy for structural assignment with a low computational cost.