({[(3S,6aR,6R)-6-{[(E)-azepan-1-ylmethylidene]amino}-2,2-dimethyl-5-oxo-3,5,6,6a-tetrahydro-2H-azeto[2,1-b][1,3]thiazol-3-yl]carbonyl}oxy)methyl (3S,6aR,6R)-6-{[(E)-azepan-1-ylmethylidene]amino}-2,2-dimethyl-5-oxo-3,5,6,6a-tetrahydro-2H-azeto[2,1-b][1,3]thiazole-3-carboxylate