Synthesis of two carboxylic haptens for raising antibodies to 25-hydroxyvitamin D3 and 1α,25-dihydroxyvitamin D3

Hapten derivatives of 25-hydroxyvitamin D3 and 1α,25-dihydroxyvitamin D3 were synthesized using the Wittig–Horner approach. Both haptens bearing a carboxylic group at the side chain that can be linked to a protein for raising antibodies of potential utility for the determination of 25-hydroxyvitamin D3, 1α,25-dihydroxyvitamin D3 and 1α-hydroxylated vitamin D3 analogues.