Synthesis of β‐sitosterol‐3‐14C

Abstract
The synthesis of β‐sitosterol‐3‐14C, specific activity 5 mCi/mM, radiochemical purity ≥98 %, is described. Starting from stigmasterol, the complete synthesis consists of eleven reaction steps. It is based on methods described in the literature. For some of the steps, a considerable improvement in yield has been achieved. The actual labelling step is the condensation of 4‐oxa‐Δ5‐stigmasten‐3‐one with phenyl acetate‐14C in the presence of sodium hydride. β‐Sitosterol‐3‐14C has been obtained with a chemical yield of 23 %, based on 4‐oxa‐Δ5‐stigmasten‐3‐one. The radiochemical yield was 10.3 %. Chemical and radiochemical purities of β‐sitosterol‐3‐14C have been determined by means of thin‐layer chromatography, gas‐liquid chromatography and mass spectrometry.