6-[(1E,3Z,7E,9E)-3-Ethyl-14-hydroxy-5,9,11,13,15-pentamethyl-12-oxo-16-(5-oxo-2,5-dihydrofuran-3-yl)hexadeca-1,3,7,9-tetraen-1-yl]-5-methyl-5,6-dihydro-2H-pyran-2-one AIDS-072923 AIDS072923 Leptomycin derivative