Structure and absolute configuration of florilenalin: X-ray analysis of 4-O-acetyl-2-O-p-iodobenzoylflorilenalin

X-Ray single-crystal analysis has established the structure and absolute configuration of (IV), the 4-O-acetyl-2-O-p-iodobenzoyl derivative of florilenalin (II), a cytotoxic guaianolide from Helenium automnale L. Crystals are orthorhombic, space group P212121 with a = 14.40(2), b = 22.62(3), c = 7.37(1) Å, Z = 4. The structure was solved by the heavy-atom method and refined by full-matrix least-squares calculations to R 0.086 over 1109 reflections from photographic data. The absolute configuration was established by the anomalous dispersion effect. The cycloheptane ring adopts a chair conformation, the cyclopentane ring is in an envelope form, and the γ-lactone ring is approximately planar.

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Author Andrew T. McPhail Chemistry