In this way the silicon acts as a traceless auxiliary. (The starting material is not enantiopure but the retention of enantiomeric excess suggests that the auxiliary directs the cyclization.)
Silicon-directed Nazarov cyclizations can exhibit induced diastereoselectivity in this way. In the example below, the silyl-group acts to direct the cyclization by preventing the distant alkene from rotating "towards" it via unfavorable steric interaction.