抄録
Novel three-proton signals at δ3.6_??_2.0 in the 60 and 10OMc NMR spectra of helianginone (II) were interpreted by several analytical methods. These protons were concluded to form an isolated ABC system which contains two chemical shifts, δAC=100.2 and δBC=81.6 cps, and three coupling constants, JAB=4.9, JBC=10.2 and JCA=-14.8 cps. In this system it is very significant that JCA is negative. These protons were assigned as in the partial structure (a) of II.
