Determination of the Stereochemistry of Substituted 5-Methylenehydantoins and Thiohydantoins by ¹³C NMR and Homonuclear NOE Experiments

Abstract

Basically the aim of this work is to define the accurate configuration of the exocyclic double bond of substituted 5-methylenehydantoins and thiohydantoins which have been conceived as potential Aldose Reductase inhibitors. A previsional survey based upon the chemical shifts analysis from ¹H and decoupled ¹³C NMR spectra discloses, for a part of the family of compounds, the assignment of the Zconfiguration for unsubstituted (2,3) and N-3 substituted (6,7,9) derivatives, and the E-configuration for the N-1 substituted (8,11) ones. The qualitative study with Homonuclear NOE (8,11) and the coupling constant measuring ^{3 J}C4-C=C-H6 from coupled ¹³C NMR (1–11), lead to the assignment of the accurate configuration of the whole family's compounds in agreement with the previsional study.

Key Words:

• Methylenehydantoins
• methylenethiohydantoins
• ¹H NMR spectra
• ¹³C NMR spectra
• Homonuclear NOE
• C-H coupling constants