Abstract:The asymmetric rhodium-catalysed 1,4-addition of alkenylzirconium reagents to 2-cyclohexenone can be useful in the synthesis of 3-alkenyl-2-methylcyclohexanones, provided that formaldehyde is used in trapping the intermediate zirconium enolates. In this manner a four-step sequence leading to the two epimeric 3-hexenyl-2-methylcyclohexanones in enantiomeric form was developed.
The discovery that 1α,25-dihydroxyvitamin D 3 is effective in the inhibition of cellular proliferation and in the induction of cellular differentiation has led to a search for analogues in which these activities and the classical calcemic activity of the hormone are dissociated. In this context, the synthesis and biological evaluation are reported for six CD-ring modified structural analogues that were conceived so as to enforce a particular orientation of the 25-hydroxylated side chain. The analogues are characterized by the absence of the Cring and the presence of an unnatural six-membered D-ring.
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