The crystal structure of (S)-(–)-6-Bromo-5,7-dihydroxy-8-methyl-2-phenyl-2,3-dihydro-4H-1-benzopyran-4-one [(–)-6-bromocryptostrobin] and a 13C N.M.R. study of (±)-cryptostrobin and related substances. Revision of the structures of the natural products (±)-lawinal, unonal, 7-O-methylunonal and isoun