Synthesis of [2,2,3α,4,4-D5]CP-88,818 (tiqueside), an internal standard for a quantitative HPLC/MS assay system

A polydeuterated form of CP-88,818 (1, tiqueside) was needed as an internal standard for a quantitative HPLC/MS assay system. [2,2,3alpha,4,4-D5]CP-88,818 (11) with undetectable D0 content was synthesized in five steps from tigogenin (2). The low D0 content was achieved through two sequential incorporation procedures which gave results superior to those achieved through a single incorporation procedure. A preparatively useful procedure for removing spirostane impurities found in naturally occurring tigogenin was also discovered.