Critical steps in the tab. synthesis of calcipotriol of natural steroid raw materials were modified to develope a stable technol. process suitable for large-scale manufg. the drug. The modification consisted in a replacement of a benzothiazo substuent in the original C-22 sulfone of the universal vitamin synton with the Ph group. Use of the Ph sulfone resulted in a stabilization of the yield of its following rearrangement to calcipotriol.