Crystal structure of (1S,2R,6R,7R,8S,12S)-4,10,17-tri­phenyl-15-thia-4,10-di­aza­penta­cyclo[5.5.5.01,16.02,6.08,12]hepta­deca-13,16-diene-3,5,9,11-tetrone p-xylene hemisolvate