Synthesis of 1 α‐ and 1 β‐amino‐25‐hydroxyvitamin D 3

1α‐Amino‐25‐hydroxyvitamin D 3 is of interest because of its low calcemic effect in vivo compared to 1,25‐dihydroxyvitamin D 3 and its characteristic inhibitory activity towards sterol regulatory element binding protein (SREBP), a regulator of lipogenesis. Here we describe the construction of a novel A‐ring synthon bearing an allylic amine, in which the key reaction is an Ichikawa rearrangement of allyl cyanate generated from an allylic alcohol, which was derived from l ‐malic acid. The diastereomers were separated by silica‐gel chromatography, and a palladium‐catalyzed coupling reaction of each diastereomer with the CD‐ring synthon afforded 1α‐amino‐25‐hydroxyvitamin D 3 and 1β‐amino‐25‐hydroxyvitamin D 3 , respectively.