Synthesis of Retiferol RAD1 and RAD2, the Lead Representatives of a New Class of des-CD Analogs of Cholecalciferol

The design and total convergent synthesis are described for the leading representatives of the new class of analogs of cholecalciferol with the CD-ring system replaced with a two-carbon aliphatic spacer. The leading representatives of C21 retiferols (RAD1 and RAD2) were obtained from a ring fragment derived from vitamin D and a chain fragment obtained from S-(−)-β-citronellol.