Development of a Novel Hapten for Radioimmunoassay of the Lignan, Enterolactone in Plasma (Serum). Total Synthesis of (±)-trans-5-Carboxymethoxyenterolactone and Several Analogues

A recently developed method for the analysis of the mammalian lignan, enterolactone 1, is based on time-resolved fluoroimmunoassay (TR-FIA) using an europium chelate as a label. This RIA utilizes enterolactone derivatives carrying a carboxylic acid appendage for the production of antiserum and tracer. The synthesis of 5-carboxymethoxyenterolactone 6 and analogues 5, 7 and 8 is described, and their suitability for the method are discussed.