The Crystal and Molecular Structure of the Unusual Spiro Dihydrofuran Diterpene Nepetaefolin

The crystal and molecular structure of the spiro dihydrofuran diterpene nepetaefolin (1) has been determined. The structure was solved by direct methods analysis of data from a crystal with space group P2₁2₁2₁ and a = 11.092 ± 0.002 Å, b = 11.484 ± 0.002 Å, c = 15.379 ± 0.003 Å, Z = 4 and density p_calcd = 1.371 g/cm³. An anisotropic large-block least-squares refinement converged to a conventional residual of R = 0.042 for 2015 reflections recorded with Cu Kα radiation on an automatic four-circle diffractometer. The effects of the considerable steric interactions in this molecule on the bond lengths are discussed.