Synthesis of 23,23-Difluoro-24-nor- and 24′,24′-Difluoro-24-Homovitamin D3 Analogues and Unexpected Structure-Activity Relationships
Fumihiro Kawagoe, Hiroya Tabuchi, Taiyo Ideguchi, Yuki Okamoto, Souma Murata, Tomofumi Yatsu, Syota Yamada, Kaori Yasuda, Yusuke Akagi, Masashi Takano, Toshie Fujishima, Yoshiki Miyata, Ken’ichi Aoki, Toshiyuki Sakaki, Atsushi Kittaka
Organics · pp. 18–18 · Published 27 Apr 2026
10.3390/org7020018Abstract
We synthesized two vitamin D3 analogues, 3 and 4, which have a shortened or elongated fluoro-side-chain based on 24,24-difluoro-25-hydroxyvitamin D3 (5) using an efficient convergent approach and studied their preliminary biological activity. Both analogues exhibited greater resistance to CYP24A1-mediated metabolism than the natural 25-hydroxyvitamin D3 (6), although their stability was lower than that of 5. Analogue 3 showed an approximately 100-fold lower human vitamin D receptor (hVDR)-binding affinity compared with 5 and 6. Despite this marked reduction in VDR-binding affinity, it demonstrated an approximately 1.5-fold increase in VDR-ligand binding domain (LBD) transcriptional activation of the natural ligand 6. In contrast, analogue 4 displayed moderate VDR-binding affinity and VDR-LBD transactivation compared with 5 and 6. We found that compound 3 is a unique vitamin D analogue with a fluorinated and shortened side-chain, exhibiting low binding affinity for hVDR but potent transcriptional activity through VDR-LBD with its long half-life; thus, 3 may serve as a basic structural skeleton for advancing medicinal chemistry and drug discovery.
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