The Crystal Structure of 8β-Hydroxymethylpodocarpane-13β-carboxylic Acid Lactone: the Circular Dichroism of This and Some Related Lactones

Abstract

The title compound crystallizes in the orthorhombic space group P2₁2₁2₁ with cell dimensions of a 7.313(1), b 9.093(1), c 24.514(2) Å. The structure was solved by direct methods from diffractometer data and refined by the method of least squares to an R of 0.050; bond lengths and angles are normal although the bridged lactone ring exhibits an unexpected conformation. Circular dichroism spectra have been obtained from the title compound and five related lactones, all of which are similar in that the lactone group extended by an extra carbon atom (C-CO-O or CO-O-C) forms a 1,3 bridge across a six-membered ring. For two of the compounds, the c.d. within the region of the n → p* transition is bisignate. We conclude that the correlations between structure and n → p* c.d. sign previously adduced for bridged-ring lactones do not extend to lactones of this type.