Synthesis of novel 19-norvitamin D3 analogs with unnatural triene system

▸ New 19-norcalcitriol analogs with an unique triene system were synthesized. ▸ It was established that 9-alkylated 19-norprevitamin D analogs undergo [1,7]-H shift. ▸ Thermal isomerization of 9-ethyl-19-norprevitamin D yields exclusively 9E-isomer.