Absolute Crystal Structure Determination of Ergot Alkaloid - Dihydroergocristine Methanesulfonate Monohydrate
Dihydroergocristine methanesulfonate monohydrate crystallizes in orthorhorhombic space group P2 1 2 1 2 (No. 18) with Z = 4, a = 12.736(2) A, b = 39.089(5) A, c = 7.130(1) A, V = 3549.6(9) A 3 . The indole moiety is nearly planar, both the ergoline ring C and the tripeptide ring F addopt an envelope E 6 conformation. The ergoline ring D and the tripeptide ring E have a chair 1 C 4 conformation. The conformation of the ring G is between E 1 and 5 T 1 . The benzene ring H is planar. The structure was solved by direct methods and refined anisotropically to the final R value of 0.078 for 4219 statistically significant observed reflections [I o 1.96s( I )]. The absolute chirality was determined based on anomalous dispersion as: C4 ( R ), C8 ( R ), C6 ( R ), C17 ( R ), C25 ( S ), C24 ( S ), C19 ( S ).