Synthesis of the first 24-aminovitamin D₃ derivatives by diastereoselective conjugate addition to a chiral methyleneoxazolidinone in aqueous media.

The synthesis of the first 24-aminovitamin D₃ derivatives is reported. A stereoselective convergent synthetic approach was employed to prepare 24(S)-benzoylamino-25-hydroxyvitamin D₃ and 24(S)-benzoylamino-1a,25-dihydroxyvitamin D₃ in six steps from iodide 2 in 34% and 42% overall yields, respectively. The key step in the synthesis is a novel diastereoselective ultrasonically induced conjugate addition, promoted by the zinc–copper couple, of iodide 2 to a methyleneoxazolidinone in aqueous media. The conjugate vitamin D triene system was constructed using the Lythgoe approach.