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ABSTRACT1,25-Dihydroxycholecalciferol, the apparent active hormonal form of cholecalciferol (vitamin D3), is formed from cholecalciferol by specific and sequential hydroxylations of the sterol at carbons 25 and 1. Recently, la-hydroxycholecalciferol was synthesized and we report on its biological activity in rachitic chicks. la-Hydroxycholecalciferol is identical in potency to 1,25-dihydroxycholecalciferol in stimulation of intestinal calcium absorption; either sterol elicits a near maximal effect at a dose of 0.3-0.6 nmol. The time-course of action of lahydroxycholecalciferol also parallels that of the active metabolite 1,25-dihydroxycholecalciferol with a maximal increase in calcium transport occurring 5-10 hr after administration of sterol to vitamin D-deficient chicks.

Fluoroxy reagents are versatile and useful electrophilic fluorinating reagents. Having wide applicability in a variety of solvents they display great potential for the synthesis of specifically fluorinated analogs of bioactive molecules.