Chemistry of Heliangine

Part II. Analyses of an ABC System in the 60 and 100 Mc NMR Spectra of Helianginone

Abstract

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, δ_AC=100.2 and δ_BC=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.