- Stereocontrolled Total Syntheses of (?)-Rotenone and (?)-Dalpanol by 1,2-Rearrangement and SNAr Oxycyclizations
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The total syntheses of (?)-rotenone and (?)-dalpanol have been achieved by a group-selective, stereospecific 1,2-shift of an epoxy alcohol and SNAr cyclizations. Three oxacycles are constructed, thus illustrating a versatile synthetic route to various rotenoids.
- Nakamura, Kayo,Ohmori, Ken,Suzuki, Keisuke
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- Fe-Catalyzed Anaerobic Mukaiyama-Type Hydration of Alkenes using Nitroarenes
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Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama-type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe-catalyzed anaerobic Markovnikov-selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov-selectivity. The method features large functional group tolerance and is also applicable for late-stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
- Bhunia, Anup,Bergander, Klaus,Daniliuc, Constantin Gabriel,Studer, Armido
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p. 8313 - 8320
(2021/03/08)
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- Hydroxylated Rotenoids Selectively Inhibit the Proliferation of Prostate Cancer Cells
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Prostate cancer is one of the leading causes of cancer-related death in men. The identification of new therapeutics to selectively target prostate cancer cells is therefore vital. Recently, the rotenoids rotenone (1) and deguelin (2) were reported to selectively kill prostate cancer cells, and the inhibition of mitochondrial complex I was established as essential to their mechanism of action. However, these hydrophobic rotenoids readily cross the blood-brain barrier and induce symptoms characteristic of Parkinson's disease in animals. Since hydroxylated derivatives of 1 and 2 are more hydrophilic and less likely to readily cross the blood-brain barrier, 29 natural and unnatural hydroxylated derivatives of 1 and 2 were synthesized for evaluation. The inhibitory potency (IC50) of each derivative against complex I was measured, and its hydrophobicity (Slog10P) predicted. Amorphigenin (3), dalpanol (4), dihydroamorphigenin (5), and amorphigenol (6) were selected and evaluated in cell-based assays using C4-2 and C4-2B prostate cancer cells alongside control PNT2 prostate cells. These rotenoids inhibit complex I in cells, decrease oxygen consumption, and selectively inhibit the proliferation of prostate cancer cells, leaving control cells unaffected. The greatest selectivity and antiproliferative effects were observed with 3 and 5. The data highlight these molecules as promising therapeutic candidates for further evaluation in prostate cancer models.
- Russell, David A.,Bridges, Hannah R.,Serreli, Riccardo,Kidd, Sarah L.,Mateu, Natalia,Osberger, Thomas J.,Sore, Hannah F.,Hirst, Judy,Spring, David R.
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p. 1829 - 1845
(2020/06/05)
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- General Synthetic Approach to Rotenoids via Stereospecific, Group-Selective 1,2-Rearrangement and Dual S N Ar Cyclizations of Aryl Fluorides
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A general synthetic approach to rotenoids is described, featuring 1) stereospecific, group-selective 1,2-rearrangements of epoxy alcohols, and 2) S N Ar oxy-cyclizations of aryl fluorides. The common intermediate epoxyketone, en route to (-)-rotenone and (-)-deguelin, was prepared from d -araboascorbic acid in five steps. Also described is the conversion of (-)-deguelin into oxidized congeners, (-)-tephrosin and (+)-12a- epi -tephrosin.
- Matsuoka, Seiya,Nakamura, Kayo,Ohmori, Ken,Suzuki, Keisuke
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p. 1139 - 1156
(2019/02/26)
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- Identificatiom and Isotopic Labelling of the Diastereotopic Methyl Groups of the Phenyl-Derived 2-Hydroxyisopropyl Residues of Natural Products: the Rotenoid Dalpanol
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The 2-hydroxyisopropyl (1-hydroxy-1-methylethyl) segment derived from a prenyl residue occurs in a number of natural products, including the rotenoid dalpanol, and the aim of this work is the identification and isotopic labelling of the (pro-R) and (pro-S)-methyls of the latter compound.The identification sequence involves linkage between (4'-E)-labelled rot-2'-enoic acid and the labelled (5'S,6'R)-stereoisomer of dalpanol (5'-epidalpanol) via the (2'R,3'R)-epoxide of absolute configuration known from X-ray analysis.Dalpanol of the natural (5'R)-series is labelled in the (6'S)-methyl with deuterium by this sequence and the procedure is applicable to 3H, 13C- and 14C-labelling since such 7'-labelled specimens of rotenone, the precursors of 4'-labelled rot-2'-enoic acids, are available from our earlier work.A second labelling method employs the separable rotenone (5'R,6'S)- and (5'R,6'R)-epoxides, which are reduced with lithium aluminium deuteride, followed by reoxidation at C-12a to give both 2H-labelled (5'R,6'S)- and (5'R,6'R)-dalpanols.Oxymercuration at the 6',7'-double bond of rotenone is selective, though not specific, for the si-face, leading mainly to the (6'R)-mercuriated product.Purification of the latter, followed by reduction with sodium borotritide, provides an excellent means for the preparation of specifically radiolabelled (5'R,6'S)-dalpanol.Monitoring was by 3H NMR spectroscopy, which is more revealing than the deuterium equivalent.
- Crombie, Leslie,Kilbee, Geoffrey W.,Moffatt, Frank,Proudfoot, Geoffrey,Whiting, Donald A.
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p. 3143 - 3148
(2007/10/02)
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