Cercospora beticola toxins. Part 16. X-Ray diffraction analyses on microcrystals of three p-beticolins

The major yellow compounds extracted from the mycelium of Cercospora beticola, the beticolins, can be divided into two subgroups, the o- and the p-beticolins. It has been found that crystallogenesis conditions which allowed the X-ray analyses of the first subgroup are unsuccessful for the second. New conditions affording microcrystals for three p-beticolins, B1, B3 and B13 are described. Diffraction experiments have been performed on a synchrotron beam line; the results confirm the proposed structures for B1 and B3 and allow that of B13 to be elucidated.