Plant hormones. X. The constitution of phaseic acid; a relative of abscisic acid from Phaseolus multiflorus. An interpretation of the mass spectrum of phaseic acid and a probable structure

After a detailed examination and interpretation of the MS of phaseic acid and methyl phaseate structure (I) is preferred for this putative relative of abscisic acid from Phaseolus multiflorus. Two facts, more difficult to reconcile with this structure are an abnormally large long-range coupling and the apparent inability of phaseic acid to undergo an alkali-induced β-elimination of the epoxide oxygen to the γ- hydroxy-β-unsaturated ketone. Attempted one step conversion of methyl phaseate into methyl abscisate produced a complex but apparently identical reaction mixture to that obtained from methyl abscisate when treated under the same conditions.