Malonic ester and acetoacetic ester synthesis of 2-[11,14C]methyl-fatty acids

Suitable conditions were sought for the synthesis of various 2-[11,14C]methyl-fatty acids by malonic ester synthesis and acetoacetic ester synthesis, both involving radio-methylation with [11,14C]Ch3I. The malonic ester synthesis gave 2-[11C]methyl-fatty acids with over 60% decay-corrected yields in about 40 min and the [14C]products with somewhat higher yields at a longer time. In the acetoacetic ester synthesis, several 2-[14C]methyl-fatty acids were synthesized in 50–70% yields by the hydrolysis of the radio-methylated acetoacetates with a concentrated potassium hydroxide solution, together with by-prodcut ketones. This hydrolysis was completed in 5 min at 70°C, whereas rather drastic conditions or a longer time were needed for the thermal decarboxylation in the malonic ester synthesis.