passages.id: split_8_test_2883_passage
passages.type: progene_text
passages.text: Mechanistically , we propose these arise from a free radical intermediate in which a C-8 carbon radical displaces the 9,11-endoperoxide O-O bond to yield an 8,9-11,12-diepoxide that is finally oxygenated stereospecifically in the 13R or 15R configuration .