Synthesis of 1α,25-dihydroxyvitamin D3-26,23-lactams (DLAMs), a novel series of 1α,25-dihydroxyvitamin D3 antagonist

Novel vitamin D3 analogs having a lactam structure in their side chains, 1α,25-dihydroxyvitamin D3-26,23-lactams (DLAMs), were designed based on the principle of regulation of the folding of helix-12 in the vitamin D nuclear receptor (VDR). The new analogs were synthesized via 1,3-dipolar cycloaddition reaction and subsequent reduction of the isoxazolidine as key steps. Among the analogs, (23S,25S)-DLAM-01 (4a) and (23S,25S)-DLAM-1P (5a) bind strongly to VDR. Moreover, these analogs were found to inhibit the differentiation of HL-60 cells induced by 1α,25-dihydroxyvitamin D3.