An NMR Study on Esculetin and It's Derivatives

Abstract

The derivatives of esculetin contain hydroquinone groups that have various biological activities. In this study, the esculetin derivatives 2~14 were obtained by inducting the methoxy and hydroxyl groups into the 5, 6, 7 and 8 positions, and pheny group into the 4 position of esculetin (1), respectively. The structures of these derivatives were analyzed by the combined use of a number of nuclear magnetic resonance (NMR) spectroscopy techniques, including 1H and 13C NMR, 1H-13C HSQC and 1H-13C HMBC. The 1H and 13C NMR chemical shifts of the compounds were assigned. The effects of different substituents on the chemical shifts were discussed. The NMR shifts of esculetin derivatives were also calculated using the quantum chemical calculation method of gauge-invariant atomic orbitals (GIAO) and continuous set of gauge transformations (CSGT). And the calculated 1H and 13C NMR chemical shifts were compared with their experimental values.

Keywords

• liquid-state nuclear magnetic resonance
• assignment
• two-dimensional NMR
• esculetin
• quantum chemical calculation