24-Hydroxylated derivatives were synthesized in 24(R) and 24(S) forms by the convergent method as analogs related to 1α,25-dihydroxy-2β-(3-hydroxypropoxy)vitamin D3. In the convergent synthesis, the A-ring fragment, synthesized from diethyl D-tartarate, and the C/D-ring fragments in 24(R) and 24(S) forms (vitamin D numbering), obtained from vitamin D2 via the Inhoffen-Lythgoe diol, were coupled in moderate yields to give 1α,24(R),25-trihydroxy-2β-(3-hydroxypropoxy)vitamin D3 and 1α,24(S),25-trihydroxy-2β-(3-hydroxypropoxy)vitamin D3. In preliminary biological evaluations, 24-hydroxylation of 1α,25-dihydroxy-2β-(3-hydroxypropoxy)vitamin D3 caused weakened affinity to vitamin D binding protein in vitro and less calcemic activity in vivo compared to the parent compound. While the affinity to vitamin D receptor in 24(R) epimer was sustained, the affinity in 24(S) epimer was less than that of the parent compound.
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