(4S)-1-tert-Butyldimethylsilyl-4-<(1S,2S)-1,2-(dimethylmethylenedioxy)-3-<1-<(3S)-3,4-dihydro-8-methoxy-1-oxo-1H-2-benzopyran-3-yl>-3-methylbutyl>amino-3-oxopropyl>azetidin-2-one