(R)-2-[(3S,4S)-3-[(R)-1-(tert-;-methylazetidin-2-one;beta-Methylazetidin-2-one;1-BMA;Butyldimethylsilyloxyethylcarboxyet;Intermediate of Meropenem;2-Azetidineacetic acid, 3-[(1R)-1-[[(1,1-dimethylethyl)dimethylsilyl]oxy]ethyl]-a-methyl-4-oxo-, (aR,2S,3S)-;1-Bma Or 4-Bma