- Diastereoselective synthesis of chiral 1,3-cyclohexadienals
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A novel approach to the production of chiral 1,3-cyclohexadienals has been developed. The organocatalysed asymmetric reaction of different β-disubstituted-α,β-unsaturated aldehydes with a chiral α,β-unsaturated aldehyde in the presence of a J?rgensen-Hayashi organocatalyst provides easy and stereocontrolled access to the cyclohexadienal backbone. This method allows for the synthesis of potential photoprotective chiral 1,3-cyclohexadienals and extra extended conjugation compounds in a simple manner.
- Urosa, Aitor,Tobal, Ignacio E.,de la Granja, ángela P.,Carmen Capitán,Moro,Marcos, Isidro S.,Garrido, Narciso M.,Sanz, Francisca,Calle, Emilio,Díez, David
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- Intramolecular Aza-Diels-Alder Cyclization of a Dimerized Citral with Anilines Catalyzed by InCl3
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A series of aza-polycyles containing octahydroacridine core were prepared via an intramolecular aza-Diels-Alder reaction of a dimerized citral with various aromatic amines. This reaction is efficiently catalyzed by InCl3 at ambient temperature
- Chen, Yijang,Ramanathan, Mani,Liu, Shiuh-Tzung
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p. 761 - 765
(2015/10/05)
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- Synthesis of the Polycyclic Ring Systems of Artocarpol A and D
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(Equation Presented) The first synthesis of the polycyclic ring systems of artocarpol A and D has been accomplished. These natural products were isolated recently from the root bark of Artocarpus rigida, and artocarpol A has been shown to have potent anti
- Paduraru, M. Peggy,Wilson, Peter D.
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p. 4911 - 4913
(2007/10/03)
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- A Racemic Diterpene from the Marine Bryozoan Flustra foliacea, Natural Product or Artefact?
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A monocyclic diterpene aldehyde, 4.6-bis(4-methylpent-3-en-1-yl)-6-methylcyclohexa-1,3-diene-1-carbaldehyde (1), was isolated from the marine bryozoan Flustra foliacea (L.) by gas phase extraction.The structure was established from extended spectroscopic studies allowing a complete assignment of 1H and 13C NMR spectra.Three isomeric trace diterpenes were detected in the extract.Since 1 was racemic it might arise from condensation of citral occurring during work-up of the extract.In support of this hypothesis, 1 was formed as the main product on base-catalyzed dimerisation of citral in vitro and the three isomeric compounds were formed as by-products or arose from decomposition of 1.
- Holst, Pia Bachmann,Anthoni, Uffe,Christophersen, Carsten,Nielsen, Per Halfdan,Bock, Klaus
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p. 765 - 768
(2007/10/02)
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- The proline and β-lactoglobulin mediated asymmetric self-condensation of β-ionylideneacetaldehyde, retinal and related compounds
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Proline was found to effectively mediate the asymmetric reaction of β-ionylideneacetaldehyde 1A, retinal and related α,β-unsaturated aldehydes to form their corresponding self-condensation products in reasonable enantiomeric excess (up to 65% ee). This sa
- Asato,Watanabe,Li,Liu
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p. 3105 - 3108
(2007/10/02)
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- Cycloaddition Reaction of Citral with Methyl Acrylate
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Reaction of citral with methyl acrylate in the presence of sodium hydride and subsequent work-up in neutral and acidic media afford the cycloaddition products.The structure and stereochemistry of these products have been discussed.
- Taneja, S. C.,Koul, S. K.,Dhar, K. L.
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p. 769 - 770
(2007/10/02)
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- Dimerisation of Citral
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3,7-Dimethylocta-2,6-dienal (citral) gives a dimeric product on reaction with sodium hydride in dry ether.The structure and stereochemistry of the product has been discussed.
- Taneja, S. C.,Koul, S. K.,Dhar, K. L.
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p. 482 - 483
(2007/10/02)
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- STEREOCONTROLLED SYNTHESIS OF CONJUGATED POLYENE ISOPRENOIDS USING PHOSPHINE OXIDE ANION INTERMEDIATES
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The potential for the Horner-Wittig reaction in the stereocontrolled synthesis of conjugated polyene isoprenoids is investigated.It is shown that metallations of the Z- and E-phosphine oxides (4 and 5), followed by reaction with Z- and E-citrals lead, in single steps, to the corresponding isomeric pentaenes (6) showing complete preservation of the Z- and E-geometries in the starting materials.Although the single step reactions leading to 6 proceed in low overall yields (10-20percent), the olefinations occur with >98percent E-stereoselectivity.Isolation of the intermediate β-hydroxyphosphine oxides (e.g. 14), followed by subsequent treatment with s odium hydride in dimethylformamide, demonstrate that these features of the reaction are associated largely with the remarkably slow rates of elimination from the erythro-intermediates in comparison with the threo-intermediates.Condensation between 4 and the ester-aldehyde (20) leads to the Z-6 ester 21 (34percent).After conversion of 21 into the tetraenal (25), reaction with the phosphine oxide (26), followed by separation of the erythro-β-hydroxy-phosphine oxide intermediate 27 and treatment with NaH in DMF, leads to the di-Z-octaene (28).The octaene 28 shows closely similar spectral data to those found in natural di-Z-phytofluene (2) isolated from fruit of the Tangerine tomato, Lycopersicon escalentum var.In a similar manner, reaction between the Z-phosphine oxide (4) and the dialdehyde (29) produces the di-Z-nonaene (33) which has the same chromophore as that found in di-Z-ζ-carotene (3) from Tangerine tomato fruits.
- Clough, John M.,Pattenden, Gerald
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p. 3911 - 3920
(2007/10/02)
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