Noncalcemic, antiproliferative, transcriptionally active, 24-fluorinated hybrid analogues of the hormone 1α,25-dihydroxyvitamin D3.: Synthesis and preliminary biological evaluation

Four new hybrid analogues of 1 alpha,25-dihydroxyvitamin D-3 (1) have been synthesized in a convergent manner by joining A-ring and C,D-ring fragments. Each hybrid analogue, having a noncalcemic 1-hydroxymethyl group and a potentiating 16-ene 24,24-difluorinated C,D-ring side chain, was designed to be lipophilic and inert toward 24-hydroxylase enzyme catabolism. Each hybrid analogue with 1 beta,3 alpha-substituent stereochemistry (i.e., analogues 3b and 4b) showed a pharmacologically desirable combination of in vitro high antiproliferative activity in two different cell lines and high transcriptional activity with also low calcemic activity in vivo.