Click the reaction arrow in sequence to view the 3D models and animations respectively.
Allylic 1,3-strain ensures that the lowest energy conformation has the hydrogen on the allylic centre eclipsing the Z-methyl group. The peroxyformic acid approaches the face that is not hindered by the trimethylsilyl group to produce the anti epoxide.
Examine the interactive energy diagram for the starting Z-allyl silane.