(4R)-(-)-2-thioxothiazolidine-4-carboxylic acid (raphanusamic acid).

The title acid, C4H5NO2S2, crystallized in the noncentrosymmetric space group P2(1)2(1)2(1) with one molecule as the asymmetric unit. Two hydrogen bonds occur, namely, N--H...O, with a donor-acceptor distance of 2.850 (2) A, and O-H...S (resonance induced), with a donor-acceptor distance of 3.318 (2) A; both H atoms involved are ordered. These two types of bonds link a given molecule to four neighbors, the molecules linked being of space-group symmetry types 1 and 3, or 2 and 4. These two subsets of molecules alternate in layers along c. Three significant C-H...O interactions occur, one of which crosslinks the subsets just described to produce a three-dimensional network of linked molecules. The absolute structure is determined.