A. Danilovski, M. Vinković, J. Herak
Apr 15, 1999
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Journal
Acta Crystallographica Section C-crystal Structure Communications
Abstract
The X-ray structure analyses of the two optically active penam derivatives, (2S,4S,5R,6S)-2-benzylcarbamoyl-6-bromo-3,3-dimethyl-4-thia-1-azabicyclo[3.2.0]heptan-7-one 4-oxide hydrate, C 15 H 17 BrN 2 O 3 S.H 2 O, (I), and (5R)-3-benzylimino-2-isopropylidene-4-thia-1-azabicyclo[3.2.0]heptan-7-one, C 15 H 16 N 2 OS, (II), have been determined in order to ascertain their absolute configurations. Both compounds adopt the open-book conformation for the fused β-lactam and thiazolidine rings. The β-lactam ring is in a distorted planar conformation, while the thiazolidine ring is in an envelope conformation. The pyramidalization effect of the N1 atom in both compounds has been characterized by a displacement of the N atom from the plane of its substituents: the N atom is displaced 0.344 (5) and 0.350 (5) A in molecules A and B of compound (I) and 0.410 (5) A in compound (II).