Byrne, LT, Cannon, JR, Gawad, DH, Joshi, BS, Skelton, BW, and Toia, RFWAH
The crystal structure of (S)-(-)-6-bromo-5,7-dihydroxy-8-methyl-2-phenyl-2,3-dihydro-4H-1-benzopyran-4-one [(–)-6-bromocryptostrobin] (11) has been determined by X-ray diffraction from diffractometer data at 295 K and refined by block diagonal least squares to a residual of 0.050 (810 'observed' reflections). Crystals of (11) are tetragonal, P43212, a 7.849(4), c 46.83(2) , Z 8. The crystallographic data are consistent with the S configuration previously proposed for (–)-cryptostrobin (10). The 13C n.m.r, spectra of ()-cryptostrobin and()-strobopinin also lead to the structures (1) and (6), respectively. This work has enabled the structures proposed for the natural products ()-lawinal, unonal, 7-O-methylunonal and isounonal to be revised to (8), (14), (15) and (12), respectively.