Received 14 November 2012
The title molecule, C21H25NO7, has four stereogenic centres and crystallized as a racemate. It consists of enantiomeric pairs with the relative configuration rac-(1R*,2S*,3R*). The cyclohexenone ring adopts an envelope conformation; the dimethyl-substituted C atom lies 0.640 (1) Å out of the mean plane formed by the rest of the ring atoms (r.m.s. deviation = 0.016 Å). The oxacyclohexene ring adopts a half-chair conformation, the hydroxy- and carboxyl-substituted C atoms lying -0.336 (1) and 0.419 (1) Å, respectively, out of the mean plane formed by the rest of the ring atoms (r.m.s. deviation = 0.002 Å). In the crystal, O-HO hydrogen bonds link the molecules into a chain along the c-axis direction.
For general background to 2H-chromenes and their derivatives, see: Cai (2008); Valenti et al. (1993); Hyana & Saimoto (1987); Tang et al. (2007). For their anticancer activity, see: Afantitis et al. (2006); Cai (2007). For puckering parameters, see: Cremer & Pople (1975).
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: AA2078 ).
We thank Baku State University and Vladimir State University for supporting this study.
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