Journal ArticleDOI
[4+2] and [2+2] Photocycloadditions of 1,2-diketones to glycal and hydroxyglycal esters ☆
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In this paper, photocycloadditions of phenanthrenequinone 1 and acenaphthenequinone 16 to 3,4,6-tri-O -acetyl-d-glucal proceeded with distinctly different regioselectivities: 1 preferentially adds with both carbonyl oxygens to give the [4+2] cycloadduct, a 1- O,2- O -annelated α- d -glucoside (50%Abstract:
Photocycloadditions of phenanthrenequinone 1 and acenaphthenequinone 16 to 3,4,6-tri- O -acetyl- d -glucal proceeded with distinctly different regioselectivities: 1 preferentially adds with both carbonyl oxygens to give the [4+2] cycloadduct, a 1- O ,2- O -annelated α- d -glucoside (50% [ Chem. Ber. 1952 , 85 , 531]), while 16 reacts with only one carbonyl group to exclusively yield the [2+2] addition product, a 1- C ,2- O -oxetano-α- d -glucoside (86%). 2-Hydroxyglucal esters 11 and 12 also undergo photoadditions with 1 to give the cis -1,4-dioxane-fused cycloadducts 13 and 14 , whilst 16 fails to react. Structural and configurational assignments rest on NMR data and an X-ray analysis of spiro-pyranooxetane 18 .read more
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Synthesis of Aryl, Glycosyl, and Azido Septanosides through Ring Expansion of 1,2-Cyclopropanated Sugars
TL;DR: The generality of the oxyglycal ring-expansion method to prepare septanosides, possessing different substituents at their reducing ends is consolidated.
Journal ArticleDOI
Synthesis and nonenzymatic template-directed polymerization of 2'-amino-2'-deoxythreose nucleotides.
TL;DR: A novel synthesis of 2′-amino modified TNA nucleosides (2′-NH2-TNA) is developed based on a cycloaddition reaction between a glycal and an azodicarboxylate, followed by direct nucleosidation of the cycloadduct.
Journal ArticleDOI
Photoaddition Reactions of 1,2-Diketones with Silyl Ketene Acetals. Formation of β-Hydroxy-γ-ketoesters
Dae Won Cho,Hyang-Yeol Lee,Sun Wha Oh,Jung Hei Choi,Hea Jung Park,Patrick S. Mariano,Ung Chan Yoon +6 more
TL;DR: The Claisen-type condensation process, following an SET desilylation pathway and predominating when the photoreactions are carried out in the polar solvent acetonitrile, represents an efficient method to prepare a variety of diversely substituted beta-hydoxy-gamma-ketoesters.
Journal ArticleDOI
Photo-Induced Cycloaddition Reactions of α-Diketones and Transformations of the Photocycloadducts
TL;DR: The diverse photo-cycloaddition pathways found in the photocycloadditions of o-diones leading to various photocyCloadducts and the potential applications of these reactions via further transformation reactions of the adducts are discussed.
Journal ArticleDOI
Sustainable Synthesis of Chiral Tetrahydrofurans through the Selective Dehydration of Pentoses
TL;DR: Through use of a hydrazone-based strategy, l-arabinose was selectively dehydrated to form a chiral tetrahydrofuran on a multi-gram scale without the need for protecting groups, and this approach was extended to other biomass-derived reducing sugars and the mechanism of the key cyclization investigated.
References
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Journal ArticleDOI
Calotropis‐Glykoside, vermutliche Teilstruktur.. Glykoside und Aglykone, 321. Mitteilung
TL;DR: In this paper, a new formulae for the 7 Calotropis glycosides: calactin, calotropin, uscharidin (19), calotoxin (20), procerosid (21), uscharin, and voruscharin (32).
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Cardenolide glycosides of the asclepiadaceae. New glycosides from asclepias fruticosa and the stereochemistry of uscharin, voruscharin and calotoxin
TL;DR: In this article, the chirality at C-3′ of uscharin (3b), voruscharin, and 19-deoxyuscharin(1b) was established.
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Photoaddition von Phenanthrenchinon-(9.10) an benzocyclische Olefine zu Keto-oxetanen als neuartige Cycloadditionsreaktion der Chinone
TL;DR: In this paper, the bisher ubersehene C3O-Cycloaddition einzelner carbonylgruppen von o-Chinonen fuhrt zu Oxetanen with α-standigen Ketogruppen.
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Cardenolides of Asclepias syriacaL., Probable Structure of Syrioside and Syriobioside. Glycosides and aglycones, 334th communication†‡
TL;DR: The Asclepias syriaca is a Futterpflanzen, auf denen die Larven von Schmetterlingen leben, welche die Cardenolide der Nahrung zu speichern vermogen and dadurch von der Vertilgung durch insektenfressende Tiere (bes. A. Vogel) teilweise geschutzt sind as discussed by the authors.