Molecular conformations. Part VI. The structure of withaferin A: X-ray analysis of withaferin A acetate p-bromobenzoate
- 1 January 1968
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society B: Physical Organic
- p. 962-972
- https://doi.org/10.1039/j29680000962
Abstract
X-Ray crystal-structure analysis of withaferin A acetate p-bromobenzoate, C37H43BrO8, has established the constitution and absolute stereochemistry of withaferin A, a novel tumour-inhibiting 5β-steroidal lactone isolated from Acnistus arborescens. The crystals are orthorhombic, of space group P212121, with eight molecules of the p-bromobenzoate and four molecules of ethyl acetate in a unit cell of dimensions a = 14·74, b = 40·35, c= 12·95 Å. The atomic co-ordinates were determined by Fourier and least-squares calculations. The conformation of ring A is boatlike. Ring B adopts a distorted half-chair form and ring C a chair form. Ring D deviates slightly from the envelope from in which C(13) is the out-of-plane atom.Keywords
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