Side Chain Analogs of Vitamin

In an effort to elucidate the structural requirements for biological activity of vitamin D, several groups have modified the size and/or substitution pattern of the side chain. 

Pregnenolone has been converted to the hydroxylated penta- and hexanor vitamins (75) and (76) (75). Similarly, standard conversions of 

The nor analog (79) has been found to antagonize the calcium mobilizing action of vitamin D3, but not that of 25-hydroxyvitamin D3, 

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