1-Pipeprazinecarboxylic Acid, 4-Methyl-, 7-Ester with (-)-N-(1S,2R,3E,5E,7S,9E,11E,13S,15R,19R)-7,13-dihydroxy-1,4,10,19-tetramethyl-17,18-dioxo-16-oxabicyclo(13.2.2)nonadeca-3,5,9,11-tetraen-2-yl)pyruvamide