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organic compounds
Diphenylmethyl 3,3-dimethyl-7-oxo-6-phenoxyacetamido-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate 4-oxide monohydrate, C29H28N2O6S.H2O, assumes the (S)-configuration with the penam moiety (1-azabicyclo[3.2.0]heptane-7-one) in the open conformation. The conformation of the penam moiety including the 3α-carboxyl and the 6β-acetamido groups is very similiar to that of penicillin V benzyl ester sulfoxide [Shin, Kim & Kim (1992). Acta Cryst. C48, 1449–1451], but the orientations of the terminal phenyl groups at the 6β-position with respect to the central penam moiety are different in the two compounds. Acetamido N9 forms an intramolecular three-centred hydrogen bond with sulfoxide O1 and phenoxy O13 atoms [N9O1 2.839 (4), N9O13 2.554 (4) Å]. The molecules are linked along the a axis via hydrogen bonds involving water molecules [O1OwO11].