CRYSTAL AND MOLECULAR-STRUCTURE OF 3,6,14,16-TETRAHYDROXYSPIRO[1,5]GRAYANOTOXIN-5-ONE

The three-dimensional structure of a grayanotoxin II derivative, 6,14, 16-tetrahydroxyspiro[1,5]-grayanotoxin-5-one, has been determined by X -ray diffraction at room temperature. The structure was solved by dire ct methods and refined by the full matrix least-squares method to a fi nal R=0.043 for 1436 independent reflections with F(o) greater-than-or -equal-to 3sigma(F(o)). The molecule is based on a tetracyclic structu re and consists of two six-membered and two five-membered rings. The a bsolute configuration at C(l) atom (spiro atom) was determined as R on the basis of internal comparison with the absolute structure of graya notoxin II.