[Theoretical study on nuclear magnetic resonance spectra of the four kinds of curcumin analogues].

Abstract The structure of four kinds of curcumin analogues was optimized at the level of B3LYP/6-31G(d, p), under which the stability was verified by means of vibration analysis. Moreover, NMR spectra of urcumin analogues compounds were studied at the level of B3LYP/6-311G(d,p) by GIAO method. The results show that the structure of four kinds of compounds, a larger conjugated system, has good planarity. Because of introducing hydroxyl and methoxy, the compound-B/C/D-C3, C4 and compoud-A and compound-D-Cs have greater 8 value. delta value of compound-A-C4. C4 is relatively smaller, and delta value of C3 is relatively larger. In the conjugated carbonyl compounds, compared with the acetaldehyde delta value (201 ppm), carbonyl C13 delta value (183 ppm) decreases relatively, C(11, 15) (alpha-carbon) delta value(122 ppm) decreases relatively, and C(9, 17) (beta-carbon) delta value(145 ppm) increases relatively. Finally, the correlation between experimental delta value and theoretical delta value of the 1H NMR was analyzed through the linear regression method. Results show that they have good correlation, and the experimental values coincide with the theoretical values.