- A Novel Synthesis of (R)- and (S)-4-Hydroxytetrahydrofuran-2-ones
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A practical synthesis of (R)- and (S)-4-hydroxytetrahydrofuran-2-ones is accomplished starting from L-ascorbic acid and D-isoascorbic acid, respectively.
- Tanaka, Akira,Yamashita, Kyohei
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- Asymmetric Synthesis of α,β-Unsaturated δ-Lactones through Copper(I)-Catalyzed Direct Vinylogous Aldol Reaction
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A simple methodology for the asymmetric synthesis of chiral α,β-unsaturated δ-lactones was achieved by copper(I)-catalyzed direct vinylogous aldol reaction (DVAR) of β,γ-unsaturated esters and various aldehydes, including aromatic aldehydes, heteroaromatic aldehydes, α,β-unsaturated aldehydes, and aliphatic aldehydes. For aromatic and heteroaromatic aldehydes, a one-pot reaction consisting of DVAR, isomerization of the unsaturated carbon-carbon double bond from (E)-form to (Z)-form, and subsequent intramolecular transesterification was required to get the lactones in moderate to high yields with high enantioselectivity. For α,β-unsaturated and aliphatic aldehydes, the DVAR proceeded directly to afford the lactones in moderate yields with high enantioselectivity. In the DVAR, various functional groups were well tolerated. Moreover, the methodology was nicely applicable to the aldehyde group distributed in natural products, derivatives of natural product, and derivatives of drug molecules (atomoxetine and naproxen). The mechanism studies revealed that α-addition was reversible and not favored, which accounted for the excellent regioselectivity in the DVAR. The copper(I)-dienolate species generated through deprotonation was proposed to form an equilibrium with an allylcopper(I) species, which reacted with aldehydes to afford the DVAR products through a catalytic asymmetric allylation of aldehydes. Finally, the robustness of the present reaction was demonstrated by a gram-scale reaction, and the utility of the present methodology was showcased by the formal asymmetric synthesis of ezetimibe and fostriecin.
- Zhang, Hai-Jun,Yin, Liang
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supporting information
p. 12270 - 12279
(2018/09/25)
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- Stereoselective synthesis of tetrahydropyranyl diarylheptanoids (-)-centrolobine and (+)-centrolobine
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A versatile chiron approach to the tetrahydropyranyl diarylheptanoid natural products (-)-centrolobine and (+)-centrolobine has been described. The use of an aldol reaction followed by reductive etherification for the formation of tetrahydropyran ring is of importance. Georg Thieme Verlag Stuttgart · New York.
- Reddy, Chada Raji,Madhavi, Pasupulety Phani,Chandrasekhar, Srivari
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experimental part
p. 123 - 126
(2011/02/26)
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- Synthetic studies on halichondrin B, an antitumor polyether macrolide isolated from a marine sponge. 9. Synthesis of the C16 - C36 unit via stereoselective construction of the D and E rings
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The C16 - C36 unit of halichondrin B was stereoselectively synthesized via the aldol condensation of two C16 - C26 esters with the previously synthesized C27 - C36 aldehyde followed by E ring construction. The C16 - C26 esters were prepared starting from (2S)-3-hydroxy-2-methylpropionic acid and L-tartaric acid via construction of the D ring by iodoetherification.
- Horita, Kiyoshi,Nagasawa, Masaaki,Sakurai, Youji,Yonemitsu, Osamu
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p. 1199 - 1216
(2007/10/03)
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- Synthesis of medium ring ethers. 5. The synthesis of (±)-laurencin
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The enantioselective synthesis of (+)-laurencin 1 has been achieved in 27 steps from (R)-malic acid 20. The key steps involved methylenation of the lactone 49 followed by intramolecular hydrosilation of the enol ether 14 (Scheme 11) and one carbon homologation of the diol 13 to give the key ethyl substituted cyclic ether 59 (Scheme 13). The lactone 49 was obtained by two efficient routes, namely a Claisen ring expansion (Scheme 3) followed by cl-hydroxylation (Scheme 6) and a Yamaguchi lactonization (Scheme 11). Elaboration of the (E)-pentenynyl side chain (Scheme 18) and introduction of bromine (Scheme 19) completed the synthesis of (+)-laurencin 1.
- Burton, Jonathan W.,Clark, J. Stephen,Derrer, Sam,Stork, Thomas C.,Bendall, Justin G.,Holmes, Andrew B.
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p. 7483 - 7498
(2007/10/03)
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- Preparation of Derivatives of (R)-1,2,4-Butanetriol from L-Ascorbic Acid
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Methyl 3,4-O-isopropylidene L-threonate (3), obtained from L-ascorbic acid, was converted to its O-phenyl thiocarbonate 4.Deoxygenation of 4 with tri-n-butyltin hydride gave the protected 3,4-dihydroxybutanoate 5, which was converted to the (R)-1,2,4-butanetriol derivatives 6 and 7.
- Luk, Kin-Chun,Wei, Chung-Chen
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p. 226 - 228
(2007/10/02)
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