- Clickable Vitamins as a New Tool to Track Vitamin A and Retinoic Acid in Immune Cells
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The vitamin A derivative, retinoid acid (RA) is key player in guiding adaptive mucosal immune responses. However, data on the uptake and metabolism of vitamin A within human immune cells has remained largely elusive because retinoids are small, lipophilic
- Bos, Amelie V.,Erkelens, Martje N.,Koenders, Sebastiaan T.A.,van der Stelt, Mario,van Egmond, Marjolein,Mebius, Reina E.
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- Asymmetric Reductive Carbocyclization Using Engineered Ene Reductases
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Ene reductases from the Old Yellow Enzyme (OYE) family reduce the C=C double bond in α,β-unsaturated compounds bearing an electron-withdrawing group, for example, a carbonyl group. This asymmetric reduction has been exploited for biocatalysis. Going beyond its canonical function, we show that members of this enzyme family can also catalyze the formation of C?C bonds. α,β-Unsaturated aldehydes and ketones containing an additional electrophilic group undergo reductive cyclization. Mechanistically, the two-electron-reduced enzyme cofactor FMN delivers a hydride to generate an enolate intermediate, which reacts with the internal electrophile. Single-site replacement of a crucial Tyr residue with a non-protic Phe or Trp favored the cyclization over the natural reduction reaction. The new transformation enabled the enantioselective synthesis of chiral cyclopropanes in up to >99 % ee.
- Heckenbichler, Kathrin,Schweiger, Anna,Brandner, Lea Alexandra,Binter, Alexandra,Toplak, Marina,Macheroux, Peter,Gruber, Karl,Breinbauer, Rolf
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supporting information
p. 7240 - 7244
(2018/06/15)
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- Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(-)-myrtenol nitrate
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Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a 'halide for nitrate' substitution. Employing readily available starting materials, reagents and Horner-Wadsworth-Emmons chemistry the synthesis of easily separable, synthetically versatile 'key building blocks' (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, 'off the shelf' materials. Exploiting their reactivity we have studied their ability to undergo an 'allylic halide for allylic nitrate' substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates ('isoprene nitrates') in 66-80% overall yields. Using NOESY experiments the elucidation of the carbon-carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our 'halide for nitrate' substitution chemistry we outline the straightforward transformation of (1R,2S)-(-)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(-)-myrtenol nitrate.
- Bew, Sean P.,Hiatt-Gipson, Glyn D.,Mills, Graham P.,Reeves, Claire E.
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supporting information
p. 1081 - 1095
(2016/07/06)
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- Biomimetic synthesis of fused polypyrans: Oxacyclization stereo- and regioselectivity is a function of the nucleophile
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(Matrix presented) The stereoselectivity of Lewis acid-induced endo-regioselective oxacyclizations of 1,4-diepoxides is dependent upon the nature of the terminating nucleophile. For instance, the tert-butyl carbonate-substituted diepoxide of 3,6-dimethylhepta-2,5-dien-1-ol provides a cis-fused bicyclic product, whereas the N,N-dimethylcarbamate derivative affords the trans-fused diastereomer. Stereospecific and regioselective conversion of the tertiary carbamate-terminated 1,4,7-triepoxide (I) to tricyclic all-trans-fused polypyran (II) is also demonstrated.
- Bravo, Fernando,McDonald, Frank E.,Neiwert, Wade A.,Do, Bao,Hardcastle, Kenneth I.
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p. 2123 - 2126
(2007/10/03)
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- New retinoid analogs from δ-pyronene, a natural synthon
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δ-Pyronene (1), a readily available terpenic synthon, is an excellent raw material for the preparation of numerous terpenic intermediates. Original retinoid analogs such as 'iso'-retinyl acetate (5), 'iso'-retinal (6) and ethyl 'iso' retinoate (7), in which the cyclogeranyl moiety is functionalized in an unusual position, were prepared from δ-pyronene.
- Lambertin, Frederic,Wende, Martin,Quirin, Marie Jeanne,Taran, Martine,Delmond, Bernard
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p. 1489 - 1494
(2007/10/03)
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- A SHORT AND CONVERGENT ENENTIOSELECTIVE SYNTHESIS OF (3S)-2,3-OXIDOSQUALENE
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A very useful synthesis of (3S)-2,3-oxidosqualene from geraniol, farnesol and E-1-bromo-4-chloro-3-methyl-2-butene is described which makes use of enantioselective and catalytic dihydroxylation of geranyl acetate and two E-stereospecific allylic coupling reactions mediated by E-prenylbarium reagents.
- Corey, E. J.,Noe, Mark C.,Shieh, Wen-Chung
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p. 5995 - 5998
(2007/10/02)
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