Maxacalcitol (OCT) (1), the 22-oxa-derivative of 1α, 25-dihydroxyvitamin D3, has been discovered as a promising candidate for the treatment of antihyperparathroidism and antipsoriatic by our medicinal chemistry research team. In order to enable the development, our process research group has made efforts for its practical large-scale production which allowed successful launch of OCT (1) as an antihyperparathroidism agent in 2000 and as an antipsoriatic agent in 2001. This article describes aspects of the efforts of the process research team making the present industrial production of OCT (1) possible on the basis of the initial synthesis carried out by the medicinal research group.
