Lumisterin steroid

In the synthesis of lumisterin steroid a D ABCD approach was used [151]. A key step is the Co-induced cyclization of cyclopentanoid ene-diynes prepared by thioalkylation of 2,3-substituted cyclopentanone zinc enolates with a-chlorosulfides. 

The cobalt-catalyzed [2+2+2] cycloaddition of 4-hydroxy-substituted enediynes [152] that has been implemented in the synthesis of 2-hydroxy substituted decahydrophenanthrenes [153] has shown that the hydroxy group in the propargyl position tolerates the chosen reaction conditions. So, this approach could be an appropriate route to hydrogenated trans-phenanthrenes, which are the ABC cores of ergosterin and lumisterin steroids. This was a reason to consider the diastereoselective synthesis of (3S)-hydroxyandrosta-5,7-diene-17-ones 2.307, the precursors of vitamin D, via a D ABCD approach. 

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