Permethylation for mass spectrometry: Rearrangements of ester linkages and use of potassiumt-butoxide

Thirteen selected compounds were permethylated with potassium t-butoxide in dimethyl sulphoxide and methyl iodide, a simpler procedure than those using sodium hydride but equally effective. From mass spectrometric study of the products. it emerged that carboxylic esters of methanol and of o-diphenols were at least partially rearranged, whereas those of benzyl alcohol and of a monophenol, as well as fully acylated carbohydrate-like substances, were largely not. Some anamalies of C-methylation and N-methylation were encountered.