Benzenepropanoic acid, .beta.-(benzoylamino)- .alpha.-(4-hydroxy-1,4-dioxobutoxy)-, 6,12b-bis(acetyloxy)-12-(benzoyloxy)- 2a,3,4,4a,5,6,9,10,11,12,12a,12b-dodecahydro- 4,11-dihydroxy-4a,8,13,13-tetramethyl-5-oxo- 7,11-methano-1H-cyclodeca[3,4]benz[1,2-b]oxet-9-yl ester, stereoisomer NSC600220