- Regio- and stereocontrolled hydrocyanation of chiral 2-alkylglycidamides with Et2AlCN: Synthesis of enantiomerically pure mono- and disubstituted malic acid derivatives
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The opening of the oxirane ring of glycidamides with Et2AlCN takes place under mild conditions in a completely regio- and stereoselective manner to afford β-cyano carboxamide derivatives, which are immediate precursors of mono- and disubstituted malic acid derivatives. The complete control of the regioselectivity can be rationalized as a consequence of the association of the reagent with the carboxamide group prior to intramolecular cyanide transfer.
- Garcia Ruano, Jose L.,Fernandez-Ibaez,Martin Castro, Ana M.,Rodriguez Ramos, Jesus H.,Rubio Flamarique, Ana C.
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p. 1321 - 1325
(2007/10/03)
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- Glycosides of polyenoic branched fatty acids from myxomycetes
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The determination of chemical structures of five novel compounds, i.e. one multibranched polyunsaturated fatty acid ((2E,4E,7S,8E,10E,12E,14S)-7,9,13,17-tetramethyl-7,14-dihydroxy-2, 4,8,10,12,16-octadecahexaenoic acid) and its four glycosides from seven different myxomycetes is described. The absolute configuration of both hydroxyl groups was determined. The glycosides containing glucose, mannose and rhamnose. These compounds were identified by means of 1H and 13C NMR, MS, UV and IR spectra. Three of them were identified in Arcyria cinerea (Bull.) Pers., two in A. denudata (L.) Wetts., and A. nutans (Bull.) Grev., Fuligo septica (L.) Wigg., Lycogala epidendrum (L.) Fries, Physarum polycephalum Schwein., and Trichia varia Pers. contained one of the identified glycosides each.
- ?ezanka, Tomá?
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p. 639 - 646
(2007/10/03)
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- Structure revision and assignment of absolute stereochemistry of a marine C21 bisfuranoterpene
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The C21 bisfuranoterpene (-)-isotetradehydrofurospongin-1 (6), previously isolated from a Western Australian Spongia sp., has been reisolated from a specimen of Spirastrella papilosa collected during scientific trawling operations in the Great Australian Bight. A 2D NMR analysis of 6 has prompted reassignment of the published structure 5, while degradation and chiral HPLC analysis have allowed determination of the absolute stereochemistry.
- Capon, Robert J.,Jenkins, Alister,Rooney, Francis,Ghisalberti, Emilio L.
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p. 638 - 639
(2007/10/03)
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- Pigments of Fungi. LIX - Synthesis of (1S,3S)- and (1R,3R)-austrocortilutein and (1S,3S)-austrocortirubin from citramalic acid
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The naturally occurring tetrahydroanthraquinone (1S,3S)-austrocortilutein (1) is synthesized for the first time in enantiomerically pure form by Diels-Alder cycloaddition between the functionalized butadiene derivative (8) and the chiral 1,3-dihydroxy-1,2,3,4-tetrahydro-5,8-naphthoquinone (9), the latter being derived from (R)-citramalic acid (3). The natural products (1S,3S)-austrocortirubin (2) and (1R,3R)-austrocortilutein (5) were also prepared for the first time by using the same strategy. CSIRO 2000.
- Gill, Melvyn,Harte, Michael F.,Ten, Abilio
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p. 245 - 256
(2007/10/03)
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- Asymmetric synthesis of (R)(-)-dimethyl citramalate
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An asymmetric synthesis of (R)(-)-dimethyl citramalate (1), involving halolactonization by using (S)(-)-proline as a chiral auxiliary, is reported.
- Jew, Sang-Sup,Kim, Hyun-Ah,Song, Sam-Mi,Jang, Jung-Sook,Park, Hyeung-Geun
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p. 153 - 156
(2007/10/03)
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- Asymmetric Allylation of Carbonyl Compounds with Tartrate-Modified Chiral Allylic Tin Reagents
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Chiral allylating reagents, readily generated in situ from tin(II) catecholate [SnII(O2C6H4)], allyl halides, chiral dialkyl tartrates, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), reacted smoothly with aldehydes or reactive ketones at - 78 °C in the presence of a catalytic amount of copper salts to afford the corresponding optically active homoallyl alcohols. Allylation of aromatic aldehydes and pyruvates by the present chiral tin reagents proceeded in high yields (81-99%) with high enantioselectivities (89-94%ee). In addition, both enantiomers of dimethyl citramalate were prepared from the allylation products of benzyl pyruvate.
- Yamada, Koji,Tozawa, Takashi,Nishida, Minoru,Mukaiyama, Teruaki
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p. 2301 - 2308
(2007/10/03)
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- Preparation of Both Enantiomers of Malic and Citramalic Acid and Other Hydroxysuccinic Acid Derivatives by Stereospecific Hydrations of cis or trans 2-Butene-1,4-dioic Acids with Resting Cells of Clostridium formicoaceticum
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(R)-Malic, (S)-malic, (R)-citramalic, (S)-citramalic, (2R,3S)-2-hydroxy-3-methylsuccinic and (2R,3S)-2,3-dimethyl-2-hydroxysuccinic acid were prepared on scales up to 25 mmol by stereospecific addition of water to different 2-butene-1,4-dioic acid derivatives catalyzed by resting cells of Clostridium formicoaceticum (Scheme 1).The (3R)-monodeuterio (R)- and (S)-malic acid as well as (R)- and (S)-citramalic acid were prepared using freeze-dried cells in 2H2O-buffer.The stereochemical purity of the products was in most cases >/= 99percent.
- Eck, Richard,Simon, Helmut
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p. 13641 - 13654
(2007/10/02)
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- A highly efficient synthesis of (R)- and (S)-citramalic acid
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An efficient multigram synthesis of optically pure (S)- and (R)-citramalic acid is described.
- Staring, Emiel G. J.,Moorlag, Henk,Wynberg, Hans
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p. 374 - 375
(2007/10/02)
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