Received 28 November 2012
The title compound, C21H22O4, also known as cajanine, features an intramolecular O-HO hydrogen bond between the adjacent carboxy and hydroxy groups. The benzene rings make an interplanar angle of 175.4 (2)°. In the crystal, molecules are linked by pairs of O-HO hydrogen bonds, forming inversion dimers.
Cajanine is an important component of the herb Cajanus cajan L., which is used in traditional Chinese medicine to treat osteonecrosis of the femoral head. For the total synthesis of cajanine, see: Ji et al. (2011). For the bioactivity of cajanine, see: Fu et al. (2009); Ji et al. (2011); Luo et al. (2008a,b); Zheng et al. (2007a,b); Inman & Hopp (2002); Ruan et al. (2009).
Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick 2008); software used to prepare material for publication: SHELXTL.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NG5309 ).
This work was supported by the National S&T Major Special Project on Major New Drug Innovation (2012ZX09301002-001). We also thank Professor Su-na Wang at Liaocheng University for assistance with the crystallography and help with the X-ray experiment.
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