Topic
Intramolecular reaction
About: Intramolecular reaction is a research topic. Over the lifetime, 5015 publications have been published within this topic receiving 138213 citations.
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TL;DR: In this article, the stereocontrolled total synthesis of hemibrevetoxin B has been achieved in 56 steps and 0.75% overall yield from d-mannose.
Abstract: The stereocontrolled total synthesis of hemibrevetoxin B (1) has been achieved in 56 steps and 0.75% overall yield from d-mannose. The intramolecular reaction of γ-alkoxyallylstannane with aldehyde is a key step for the present total synthesis. Thus, the BF3·OEt2-mediated reaction of 24 gave 6 as a sole product. We encountered difficulty in the synthesis of γ-alkoxyallylstannane 30 from the corresponding allyl ether 29 in which the γ-alkoxy substituent became sterically quite bulky. This problem was solved by developing the acetal cleavage method for the synthesis of γ-alkoxyallylstannanes. The cyclization of 38 proceeded smoothly to give the key intermediate 5 in a highly stereoselective manner. Construction of the α-vinyl aldehyde and (Z)-diene moieties were performed using Nicolaou's protocol.
42 citations
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TL;DR: In this article, a palladium catalyzed intramolecular Heck olefination was used to establish the C 10 C 11 connection in a highly functionalized taxane analog.
42 citations
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42 citations
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TL;DR: In this paper, a diastereoselective synthesis of a highly functionalized decalin fragment 61 of the insect antifeedant azadirachtin 1 is described.
Abstract: A diastereoselective synthesis of a highly functionalized decalin fragment 61 of the insect antifeedant azadirachtin 1 is described. An intramolecular Diels–Alder reaction of triene 15 and subsequent intramolecular aldol reaction were employed to assemble the basic carbon skeleton. A high degree of stereocontrol in the cycloaddition step was achieved by using a dimethyl(phenyl)silyl group to effect endo-selectivity. The silyl group enabled further diastereoselective elaboration and later stereospecific introduction of C(3) hydroxy functionality through oxidation with peracid. Both enantiomers of the intermediate alcohol 40 were obtained by optical resolution. The C(9)–C(10) tetrahydrofuran hemiketal moiety was introduced using a novel 6→5 ring-contraction protocol with initial formation of the δ-lactone 49 by an intramolecular Michael addition. Subsequent α-hydroxylation and methanolysis furnished the tetrahydrofuran hemiketal 50, which was converted in two steps into the fully protected enantiopure target molecule 61. Single-crystal X-ray analyses of compounds 18, 50, and (+)-53 have been carried out and the absolute configuration of compound (+)-53 determined
41 citations
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TL;DR: In this paper, the authors used a catalytic amount of Cu(OTf)2 to afford lactones and cyclic ethers, offering a practical alternative to existing catalysts.
41 citations