Synthesis and biological activity of 2-(3'-hydroxypropylidene)-1α-hydroxy-19-norvitamin D analogues with shortened alkyl side chains.

As a continuation of our efforts directed to vitamin D compounds of promising biological properties, 19-norvitamins 9-13, possessing a 3'-hydroxypropylidene fragment attached to C-2 and shortened 17β-alkyl chains, were synthesized. A new synthetic pathway providing the CD-ring ketones 20-24 is described starting from the epimeric aldehydes 25 and 26. The hydrindanones 20-24 were subjected to the Wittig-Horner reaction with the phosphine oxide 14, and the vitamin D compounds 9-13 were obtained after hydroxyl deprotection. In comparison to 1α,25-(OH)(2)D(3) (1), the prepared analogues, except for the 20R-compound 12, were only ca. 3 times less potent in binding to VDR. Compounds 9-11 and 13 exhibited HL-60 cellular activity 5-20 times lower and transcriptional activity ca. 10 times decreased related to those for the hormone 1. When tested in vivo, all the analogues showed no ability to mobilize calcium from bone, and intestinal calcium transport activity was observed only at high doses of the vitamins 10, 12, and 13.