The same behavior was observed for compound 6f,where the 1H
NMR spectra of 6f in CDCl3 showed two doublet of doublet (dd) peaks
at δ 3.11 ppm and 3.20 ppm, corresponding to the two diastereotopic
methylene protons Ha and Hb, respectively, as shown in Fig. 2. Ha
showed a doublet of doublet peak caused by couplingwith the germinal
proton Hb with 2J=13.92 Hz, then with the vicinal proton Hc with 3J=
7.32 Hz. Similarly, Hb showed a doublet of doublet peak as a result of
coupling with the germinal proton Ha with 2J = 13.86 Hz, then with
the vicinal proton Hc with 3J = 5.12 Hz. Two singlet peaks at δ
3.88 ppm and 3.91 ppm corresponding to the two methoxy groups
were observed. A quartet peak appeared at δ 4.96 ppm corresponding
to the α-proton. The peaks corresponding to the aromatic protons and
the NH appeared at the expected positions.