Acta Crystallographica Section C

Crystal Structure Communications

Volume 59, Part 2 (February 2003)

Acta Cryst. (2003). C59, o57-o59    [doi:10.1107/S0108270102022369]

Two new heterocyclic [3.3.3.0^1,5]-propellanoid compounds: 2,8-dioxatricyclo[3.3.3.0^1,5]undecane-3,7-dione and a related dimer

J. F. Tsao, S. R. Faruqi, H. W. Thompson and R. A. Lalancette

Abstract: 2,8-Dioxatricyclo[3.3.3.0^1,5]undecane-3,7-dione, C₉H₁₀O₄, (I), is the dilactone acylal of cyclopentanone-2,2-diacetic acid. Both molecules in the asymmetric unit have conformational chirality and differ principally in the flexing of the carbon ring, which produces a resolvable conformational disorder in one of the molecules. Three intermolecular C-HO close contacts exist. 7,7'-Oxybis(2,8-dioxatricyclo[3.3.3.0^1,5]undecan-3-one), C₁₈H₂₂O₇, (II), a racemate, lies on a C₂ axis and is a non-meso furanosyl furanoside dimer derived from the monoacid monoaldehyde corresponding to (I). One intermolecular C-HO close contact exists. Diminished intramolecular void space in these small propellanoids generates unusually high crystal density in both species, particularly (I).

Formula: C₉H₁₀O₄ and C₁₈H₂₂O₇

Online 11 January 2003

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