SUMMARYWe describe, herein, the first synthesis of isomerically pure title compound (6) at high specific activity. This required the development of a convenient, regiospecific synthesis of the AWWl5-ketone (x) and subsequent alkylation with methyl-[3H3] iodide. A key step in our procedure was the use of an electrochemical reduction of t h e i n t e r medi at e [ 1 4 a -m e t h y l -3 H I -1 5 -0 x 0 -dihydrolanosterol (19). This process was effected cleanly and in high yield to give (6), an important assay tool in the search for cholesterol lowering agents. This approach was found to be significantly superior to the Wolff-Kishner reduction of the corresponding 3-benzoate (a).

Benzoguinone‐[U‐14C] was synthesized in 90% yield from benzene‐[U‐14C] via a three step seguence. Conditions were developed which allowed this conversion to be accomplished in a one pot closed system. The benzoquinone‐[U‐14C] thus obtained could be reduced to hydroquinone‐[U‐14C] in quantitative yield. Preparation of benzene‐[U‐14C] is also described.