New A-ring analogs of the hormone 1α,25-dihydroxyvitamin D 3: (2′-hydroxymethyl)tetrahydrofuro[1,2- a]-25-hydroxyvitamin D 3

Abstract

Conceptually new, enantiomerically pure bicyclic tetrahydrofuro[1,2- a]-A-ring phosphine oxides (+)- 4 and (−)- 4 were successfully prepared from methyl 2-pyrone-3-carboxylate and ( S)- or ( R)-2-( tert-butyldimethylsilyloxy)methyl-2,3-dihydrofuran, respectively. In addition, (2′-hydroxymethyl)tetrahydrofuro[1,2- a]-25-hydroxyvitamin D 3 3a and 3b as new A-ring-modified analogs of the natural hormone 1α,25-dihydroxyvitamin D 3 were readily synthesized by using Lythgoe-type coupling of the A-ring phosphine oxides (+)- 4 and (−)- 4 with C,D-ring ketone (+)- 5.