rac-Ethyl 2-hydroxy-2,7,7-trimethyl-4-(4-nitrophenyl)-5-oxo-3,4,5,6,7,8-hexahydro-2H-chromene-3-carboxylate

rac-Ethyl 2-hydroxy-2,7,7-trimethyl-4-(4-nitrophenyl)-5-oxo-3,4,5,6,7,8-hexahydro-2H-chromene-3-carboxylate

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The title molecule, C21H25NO7, has four stereogenic centres and crystallized as a racemate.It consists of hbl5266ca 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 here 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—H.O hydrogen bonds link the molecules into a chain along the c-axis direction.