(-)-Isosantonic acid: alteration of the hydrogen-bonding mode by configurational inversion at a single centre in a gamma, epsylon-diketocarboxylic acid.

ZINCZUK, J.; RÚVEDA, E.A.; LALANCETTE, R.A.; THOMPSON, H.W.

ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS

International Union of Crystallography

Año: 2006 vol. E62 p. 2120 - 2122

0108-2701

The title diketo acid, (1R,3aS,6aS,7R,9S)-(-)-a,3a,7-trimethyl-5,8-dioxo-1,4-ethanoperhydropentalene-1-aceticacid (C15H20O4), is shown to aggregate in the crystal structure as acid-to-ketone hydrogen-bonding catemers, whose chains follow 21 screw axes from each carboxyl to a ketone in a neighbouring molecule [O....O = 2.7472 (13) A ° and O.....H—O = 172.7 (17)º]. Two parallel counter directional screwrelated single-strand hydrogen-bonding chains pass through the cell in the a direction. Six intermolecular C—H....O=C close contacts are found. Comparisons are drawn with a diastereomer having the opposite configuration at the methylated chiral centre adjacent to the carboxyl group.