(4R,5S)-(pivaloyloxy)methyl 3-((1-(4,5-dihydrothiazol-2-yl)azetidin-3-yl)thio)-4-methyl-5-((4R,5S)-4-methyl-6-oxo-1,3-dioxan-5-yl)-4,5-dihydro-1H-pyrrole-2-carboxylate