Synthesis of (24R)‐11α‐(4‐Carboxybutyryloxy)‐24,25‐ dihydroxyvitamin D3: A Novel Haptenic Derivative Producing Antibodies of High Affinity for (24R)‐24,25‐Dihydroxyvitamin D3.

The measurement of serum/plasma (24R)-24,25-dihydroxyvitamin D31a levels, which is one of the major metabolites of vitamin D31b, is important to clarify its physiological significance. To obtain highly specific antibodies to compound 1a which are useful for development of immunoassays, a novel haptenic derivative, (24R)-11α-(4-carboxybutyryloxy)-24,25-dihydroxyvitamin D32 was synthesized in 21 steps from a [17(20)Z]-ethylidene derivative 3 of 11α-hydroxydehydroepiandrosterone. The preparation of an immunogenic conjugate of the hapten 2 with bovine serum albumin and the properties of the resulting antibodies are also described briefly.