Stereoselective conversion of vitamin D3 into its 3β-halogenated derivatives. The synthesis of a 1α-hydroxy-3β-fluorovitamin D3 analogue

Abstract

(6R)-Hydroxy-3,5-cyclovitamin D₃ was converted with HF, HCl, and HBr into 3β-fluoro-, 3β-chloro-, and 3β-bromo-3-deoxyvitamin D₃ respectively, and with NaI–ZnCl₂ into the corresponding 3β-iodo derivative; a 3β-fluoro-1α-hydroxyvitamin D₃ analogue was prepared from 1α-hydroxyvitamin D₃ tosylate using the 3,5-cyclovitamin derivative as an intermediate.