6α,7α-epoxy-5α,17α,dihydroxy-1-oxo-22R-witha-2,24-dienolide in leaves of Withania somnifera: Isolation and its crystal structure |
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Authors: | Pankaj Bandhoria Vivek K Gupta Musarat Amina Naresh K Satti Prabhu Dutt Krishan A Suri |
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Institution: | (1) Post-Graduate Department of Physics, University of Jammu, Jammu Tawi, 180 006, India;(2) Natural Products Chemistry Division, Regional Research Laboratory, Jammu Tawi, 180 001, India |
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Abstract: | 6α,7α-epoxy-5α,17α,dihydroxy-1-oxo-22R-witha-2,24-dienolide (C28H38O6) was isolated from Withania somnifera leaves. The structure of the withanolide was established by spectral analysis and X-ray diffraction studies as withanone. The compound crystallizes in the orthorhombic space group P212121 with unit cell parameters: a = 9.191(10) Å, b = 12.858(6) Å, c = 21.400(16) Å, Z = 4. The crystal structure was solved by direct methods and refined to R = 0.0603 for 1742 observed reflections. There is positional disorder of the H atom in a hydroxy group (O5), resulting in two possible hydrogen-bond linkages. All the rings of the steroid skeleton are trans connected. Ring A exists in a half-chair conformation, ring B is intermediate between a half-chair and a sofa, ring C a distorted chair, and five-membered ring D is intermediate between a half-chair and an envelope. The δ-lactone ring E adopts a sofa conformation. The twist along the length of the steroid nucleus is negligible C19–C10…C13–C18=1.8°]. Both the hydroxy groups are involved in hydrogen bonding. |
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Keywords: | Crystal structure steroid chair envelope sofa direct methods hydrogen bond withanolide |
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