Further oxidation products of 2,2,5,7,8‐pentamethyl‐6‐chromanol

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Abstract
In order to undertake a quantitative study by high‐performance liquid chromatography of the rate of oxidation of 2,2,5,7,8‐pentamethyl‐6‐chromanol (1), the model compound of α‐tocopherol, a number of potential products were required as standards. Among these compounds were 2,2,7,8‐tetramethylchroman‐5,6‐dione (10) and 2,2,7‐trimethyl‐6‐hydroxychroman‐5,8‐dione (17), the model compounds of tocored and tocopurple, respectively. Attempts to synthesize 10 and 17 led to the isolation of 8‐hydroxymethyl‐2,2,7‐trimethylchroman‐5,6‐dione (14) and 1,2‐bis(2,2,7‐trimethylchroman‐5,6‐dione‐8‐)ethane (19) a dimer of 10. Purification by thin‐layer chromatography of the spirodimer (20) of 1 resulted in an acid‐catalyzed decomposition to 1‐(2,2,7,8‐tetramethyl‐6‐chromanol‐5‐)2‐[2‐(3‐methyl‐3‐hydroxybutyl)‐5,6‐dimethyl‐1,4‐benzoquinone‐3‐]ethane (23), a new chromanol‐quinone dimer.