Enantioselective Synthesis of (−)‐β‐Santalol by a Copper‐Catalyzed Enynol Cyclization–Fragmentation Reaction

Fehr, Charles; Magpantay, Iris; Arpagaus, Jeremy; Marquet, Xavier; Vuagnoux, Magali

doi:10.1002/ange.200903449

Cited by 22 publications

(10 citation statements)

References 64 publications

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“…d, J = 3.6 Hz, 1 H), 2.19 (dd, J = 13.9, 7.8 Hz, 1 H), 2.16 (s, 3 H), 2.06 (d, J = 3.5 Hz, 1 H), 2.03 (dd, J = 14.2, 7.4 Hz, 1 H), 1.81 (d, J = 1.3 Hz, 3 H), 1.76–1.59 (m, 4 H), 1.45–1.35 (m, 1 H), 1.28–1.21 (m, 1 H), 1.19 (ddd, J = 9.8, 1.3, 1.3 Hz, 1 H), 1.02 (s, 3 H) ppm. The 13 C spectroscopic data were identical to those of the major isomer in the previously reported 4:1 ( E , E / E , Z ) mixture 11b…”

Section: Methodssupporting

confidence: 78%

Multifold Fluorescence Enhancement in Nanoscopic Fluorophore–Clay Hybrids in Transparent Aqueous Media

Felbeck

Mundinger

Lezhnina

et al. 2015

Chemistry A European J

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Valuable emissive properties of organic fluorophores have become indispensable analytical tools in biophotonics, but frequently suffer from low solubilities and radiationless deactivation in aqueous media, that is, in biological ambience as well. In this report, nanoscaled dye-clay hybrids based on laponite, Na0.7 {(Li0.3 Mg5.5 )[Si8 O20 (OH)4 ]}, are taken advantage of to solubilize neutral dyes, which are natively not encountered in water. Previously reported efficiency and solubility bottlenecks of such hybrids can to a large extent be overcome by comparably simple chemical measures, as demonstrated here for two prominent examples, the fluorescent dyes Nile Red and Coumarin 153. On controlled co-adsorption of small bifunctional quaternary ammonium ions (Me3 N(+) C2 H5 OH and Me3 N(+) C2 H5 NH2 ) we observed an outright efficiency boost by an order of magnitude, and a 30-fold brightness gain. Even at higher concentrations, transparency and stability of the hybrid dispersions are retained, rendering them useful for employment as optically functional nanoparticles in bioassays and beyond.

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Section: Methodssupporting

confidence: 78%

Multifold Fluorescence Enhancement in Nanoscopic Fluorophore–Clay Hybrids in Transparent Aqueous Media

Felbeck

Mundinger

Lezhnina

et al. 2015

Chemistry A European J

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“…Therefore, the study on asymmetric syntheses and organoleptic properties of chiral flavours and fragrances has been a popular research subject in flavour and fragrance chemistry in recent years. [2][3][4][5][6] More and more chiral flavours and fragrances have been known with the development of asymmetric synthesis and analytic technology and the organoleptic properties of over 1170 enantiomers of chiral flavours and fragrances have been reported so far. [7] Sharpless asymmetric epoxidation (AE) has been known as one of the most efficient enantioselective epoxidation reactions of allyl alcohols.…”

Section: Introductionmentioning

confidence: 99%

Application of Sharpless asymmetric epoxidation on the preparation of the optically active flavours 3‐methylthiohexanal and 5(6)‐butyl‐1,4‐dioxan‐2‐one

Tian¹,

Sun²,

Tang³

et al. 2010

Flavour & Fragrance J

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Optically active 2,3-epoxyhexanol obtained from Sharpless asymmetric epoxidation (AE) was regioselectively reduced to 1,3-hexandiol or 1,2-hexandiol. 1,3-Hexandiol was converted to 3-mesyloxyhexyl acetate. The following reaction with CH3SK gave 3-methylthiohexanol, which was oxidized through Swern oxidation to produce 3-methylthiohexanal. 5-and 6-Butyl-1,4-dioxan-2-one were formed concurrently by the reaction of 1,2-hexandiol with 2-bromoacetic chloride and the ratio of 5-butyl isomer to 6-butyl isomer was about 1:4. The enantiomeric excess values of both enantiomers of 3-methylthiohexanal and 5(6)-butyl-1,4-dioxan-2-one were about 90%, which were very close to those of 2,3-epoxyhexanol (about 94% ee). No obvious racemization occurred during the transformation from the Sharpless AE products to the final products.

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“…Only analytical amounts of the major endo-cycloadducts could be isolated and characterized, while the crude mixture was used for the next alkylation step ( t BuOK, t BuOH, MeI, 27% yield), to furnish a complex 13 : 3 : 25 : 28 : 3 : 8 mixture regio-cis-endo-10'd 22 )/regio-cis-exo-10'd 23 )/regio-endo-10'd 24 )/endo-10d 25 )/cisexo-10d 26 )/cis-endo-10d 27 ). Further purification was unsuccessful, and the characteristic signals could only be tentatively attributed 28 ). We faced the same problem with the alkylation using EtI (33% yield) and obtained a 11 : 5 : 29 : 19 : 4 : 6 mixture regio-cisendo-10'h 29 )/regio-cis-exo-10'h 30 )/regio-endo-10'h 31 )/endo-10h 32 )/cis-exo-10h 33 21 ) For the thermal cycloaddition of (E)-11b to 9 at 1608 (4 h, 71% yield), see [24].…”

mentioning

confidence: 95%

“…were the most efficient conditions in terms of yields and diastereoselectivities ( 2 , a polar solvent, showed poorer kinetics and stereoselectivities in the case of 7 with dienophiles 5a, 5d, and 5j (Entries 31, 48, and 55), mostly due to the competing formation of a third stereoisomer.…”

mentioning

confidence: 96%

endo/exo Stereoselectivity in DielsAlder Reactions of α,β‐Dialkylated Conjugated Enals to Cyclic 1,3‐Dienes: Intermediates in the Synthesis of (−)‐β‐Santalol and Its Analogs

Chapuis

Skuy

Laumer

et al. 2014

Chemistry & Biodiversity

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Highly exo-selective [4+2] cycloadditions of cyclopenta-1,3-diene 2a to α,β-dialkyl conjugated enals 5 are compared with the analogous endo-favored Diels-Alder reaction of cyclohexa-1,3-diene 7. The exo-stereoselectivity is lower in the homologous case of methylcyclopenta-1,3-diene 9. This diastereoselectivity is discussed either in terms of a retro-homo-Diels-Alder reaction, associated with thermodynamic control, or with respect to either a competing hetero-Diels-Alder/Claisen or Cope domino pathway, or retro-Claisen/retro-hetero-Diels-Alder of the endo-homo-cycloadducts. These hypothetical mechanisms have been examined by DFT calculations at the MPW1K(CH2 Cl2 )/6-31+G** level of theory for the AlCl3 -mediated cycloadditions of 5d to 2a and 7. Application of Corey's methodology to the γ-halogeno-α-methyl-substituted dienophiles 5a and 5b allowed an enantioselective preparation of known and useful intermediates for the synthesis of either the naturally occurring (-)-β-santalol or its potentially olfactive structural analogs.

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Enantioselective Synthesis of (−)‐β‐Santalol by a Copper‐Catalyzed Enynol Cyclization–Fragmentation Reaction

Cited by 22 publications

References 64 publications

Multifold Fluorescence Enhancement in Nanoscopic Fluorophore–Clay Hybrids in Transparent Aqueous Media

Multifold Fluorescence Enhancement in Nanoscopic Fluorophore–Clay Hybrids in Transparent Aqueous Media

Application of Sharpless asymmetric epoxidation on the preparation of the optically active flavours 3‐methylthiohexanal and 5(6)‐butyl‐1,4‐dioxan‐2‐one

endo/exo Stereoselectivity in DielsAlder Reactions of α,β‐Dialkylated Conjugated Enals to Cyclic 1,3‐Dienes: Intermediates in the Synthesis of (−)‐β‐Santalol and Its Analogs

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