(10R,11R)-9-[1-Methoxycarbonyl-meth-(E)-ylidene]-7-(2-nitro-benzenesulfonyl)-10-(2-oxo-ethyl)-6,7,8,9,10,11-hexahydro-5H-7,12-diaza-cyclonona[a]indene-11,12-dicarboxylic acid 12-tert-butyl ester 11-methyl ester