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. 2008 Jul 16;130(28):9000-5.
doi: 10.1021/ja711475f. Epub 2008 Jun 21.

Ligand tuning in asymmetric hydrovinylation of 1,3-dienes: a stereoselective route to either steroid-C20 (S) or -C20 (R) derivatives

Biswajit Saha  1 , Craig R Smith, T V RajanBabu
Affiliations

Ligand tuning in asymmetric hydrovinylation of 1,3-dienes: a stereoselective route to either steroid-C20 (S) or -C20 (R) derivatives

Biswajit Saha et al. J Am Chem Soc. .

Abstract

1,3-Dienes derived from steroidal D-ring C 17-ketones undergo Ni(II)-catalyzed hydrovinylation to give 1,2- or 1,4-addition of ethylene. Using finely tuned phosphoramidite ligands, it is possible to synthesize either the C 20 ( R)- or ( S)-derivatives without mutual contamination. The proportion of the 1,4-adduct, which is also formed stereoselectively, can be minimized by optimizing the reaction conditions. Because the two alkenes in the resultant dienes have differing steric demands for many potential reactions, and are ideally juxtaposed for further D-ring functionalization, these intermediates could be useful for the preparation of biologically important compounds such as vitamin D analogs and various antitumor steroidal glycosides.

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Figures

Figure 1
Figure 1
Important Classes of Natural Products with Exocyclic Chirality with a Methyl-bearing Carbon
Scheme 1
Scheme 1
Exocyclic Stereocenters via Asymmetric Hydrovinylation
Figure 2
Figure 2
Ligands for Hydrovinylation of Steroidal 1,3-Dienes
Scheme 2
Scheme 2
Origin of 1,2- and 1,4- Adducts in the Hydovinylation Reactions
Scheme 3
Scheme 3
D-Ring Functionalization via Hydrovinylation Adducts
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See this image and copyright information in PMC

References

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