Deacetyl tenuazonic acid

The heterocycle in the title compound {systematic name: (5S)-5-[(1S)-1-methylpropyl]pyrrolidine-2,4-dione}, C8H13NO2, is planar (r.m.s. deviation for all non-H atoms = 0.008 Å). The crystal structure is stabilized by N—H⋯O hydrogen bonding.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT2937). Comment Tenuazonic acid (TA) is an Alternaria mycotoxin commonly encountered in food (Siegel, Rasenko et al., 2009;Weidenbörner, 2001). The title compound is known to be formed upon boiling of TA in 0.1 M HCl (Stickings, 1959). It is therefore a possible degradation product which might also be encountered in food matrices.

Structure Reports Online
Whereas TA itself could so far only be crystallized as its copper (II) salt (Dippenaar et al., 1977) or 2,4-dinitrophenylhydrazone (Siegel, Merkel et al., 2009), the title compound is conveniently crystallized from hexane/ethyl acetate.
Each molecule (Fig. 1) is connected to two adjacent molecules via N-H···O hydrogen bonds. Along the b axis chains of symmetry equivalent molecules are formed (Fig. 2).

Experimental
The title compound was supplied by the workgroup of Professor R. Faust (University of Kassel, Germany) by synthesis according to a literature procedure (Lebrun et al., 1988). For x-ray analysis, it was recrystallized several times from hexane:ethyl acetate 50:50 (v:v).

Refinement
The hydrogen atoms were located in difference maps but positioned with idealized geometry and refined using the riding model, with C-H = 0.98-1.00 Å or N-H = 0.90 Å and U iso (H) = 1.2U eq (C,N) or 1.5U eq (C methyl ). Fig. 1. ORTEP representation of the title compound with atomic labeling of, shown with 50% probability displacement ellipsoids.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.