5-[(1S,4R,5S,15R)-5-(3,5-difluoro-benzyl)-4-hydroxy-7-oxo-14-oxa-2,6-diaza-tricyclo[13.6.1.016,21]docosa-11,16(21),17,19-tetraen-19-yl]-hexahydro-pyrrolo[3,4-c]pyrrole-2-carboxylic acid tert-butyl ester