This derivative of triphenylphosphine is the main reagent in the second step of the synthesis, known as the Wittig Reaction. The reagent is prepared by dissolving Ph3PCH3 in THF and n-BuLi, which deprotonates the methyl group and forms a methylene group. This reacts with the ketone carbon on the original molecule, forming a cyclic transition state in the process, in order to reduce the ketone to a methylene group.