Fungal metabolites. Part VI. Crystal and molecular structure of secalonic acid A

X-Ray analysis of secalonic acid A (C32H30O14,2CH3CO2H) has confirmed the 2,2′-nature of the biphenyl linkage between the two halves of the molecule. Together with the known stereochemistry at C(6), C(6′)(I), this provides the absolute configuration of the molecule. The analysis has also indicated how the acetic acid molecules are incorporated in the crystal structure by hydrogen bonding. Estimation by n.m.r. of the torsion angle between adjacent C–OH and C–Me groups in secalonic acid A from solvent-induced changes of chemical shift was confirmed by the X-ray results.