(13r,15s)-13-methyl-16-oxa-8,9,12,22,24-pentaazahexacyclo[15.6.2.1~6,9~.1~12,15~.0~2,7~.0~21,25~]heptacosa-1(24),2,4,6,17(25),18,20-heptaene-23,27-dione