Isolation and crystal structure of lawinal.

The structure of the natural product lawinal [systematic name: (-)-(2S)-5,7-dihy-droxy-6-methyl-4-oxo-2-phenyl-chromane-8-carbaldehyde, C(17)H(14)O(5)] at 150†K is reported. The compound crystallizes with monoclinic (I2) symmetry and with Z' = 2. The absolute configuration could not be determined reliably from X-ray analysis only. However, our analysis returns the S-configuration at the C-2 position, consistent with previous stereochemical assignment from specific rotation. The independent mol-ecules form into alternating hydrogen-bonded chains with C-H⋯O=CH inter-molecular linkages that run parallel to the crystallographic a axis and are extended into the ac plane by π-π inter-actions between their phenyl substituents.