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

Abstract

2,8-dioxatricyclo[3.3.3.0(1,5)]undecane-3,7-dione, C(9)H(10)O(4), (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-H...O close contacts exist. 7,7'-Oxybis(2,8-dioxatricyclo[3.3.3.0(1,5)]undecan-3-one), C(18)H(22)O(7), (II), a racemate, lies on a C(2) axis and is a non-meso furanosyl furanoside dimer derived from the monoacid monoaldehyde corresponding to (I). One intermolecular C-H...O close contact exists. Diminished intramolecular void space in these small propellanoids generates unusually high crystal density in both species, particularly (I).

The epimeric 9-oxobicyclo[3.3.1]nonane-3-carboxylic acids: hydrogen-bonding patterns of theendoacid and the lactol of theexoacid

“…Such ring±chain tautomerism is relatively common in -and -carboxy ketones and carboxy aldehydes (Chadwick & Dunitz, 1979;Thompson et al, 1985;Dobson & Gerkin, 1996;Valente et al, 1998;Tsao et al, 2003). Although there appears to be some preference for -over -lactones (Soffer et al, 1950;Jones, 1963), examples of the latter are not lacking.…”