(2R,3R)-3-Ammonio-1-(1-methoxycarbonyl-2-methyl-1-propenyl)-4-oxoazetidine-2-sulfonate Monohydrate: a New Chiral β-Lactam Synthon

The title compound, a novel monocyclic β-lactam, was prepared and chemically characterized by IR and ¹H NMR spectroscopy and X-ray structure analysis. C₉H₁₄N₂O₆S.H₂O exists as a zwitterion crystallized with a water molecule. The four-membered lactam ring is slightly puckered, the ammonio and sulfonate groups are cis, and the aliphatic substituent is trans to these polar groups. Hydrogen bonds link the zwitterions and the water molecules into spirals parallel to the b axis, forming a two-dimensional network with base vectors along (100) and (010).

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