Figure 4.

NMR spectra of A2-GPE. (A) Proton decoupled ¹³C NMR spectra in CD₃OD. Signals appearing at 50 to 80 ppm are shown. Carbon resonances coupled with the phosphorous atom present as doublets. (B) ¹H NMR spectrum in CD₃OD. Signals within the 6.5–8.5 ppm region correspond to aromatic and olefinic protons. Critical coupling constants for the elucidation of the double bonds are presented. (C) Rotating-frame Overhauser effect spectroscopy (ROESY) spectra of A2-GPE in CD₃OD. A region showing the ROE correlations between olefinic protons and methyl protons is shown. ROE correlations appear when the two protons are sufficiently close geometrically. (D) A region of heteronuclear multiple-bond correlation spectroscopy (HMBC) spectrum of A2-GPE in CD₃OD. HMBC correlations were observed when the corresponding carbon and proton signals are within three, or occasionally four, bonds.