scholarly journals Mechanism of Stereoselective Synthesis of Push-Pull (Z)-4-Oxothiazolidine Derivatives Containing an Exocyclic Double Bond. A MNDO-PM3 Study

2002 ◽  
Vol 2002 (10) ◽  
pp. 485-489 ◽  
Author(s):  
Rade Marković ◽  
Željko Vitnik ◽  
Marija Baranac ◽  
Ivan Juranić
Keyword(s):  
Double Bond ◽  
Stereoselective Synthesis ◽  
Exocyclic Double Bond ◽  
Pm3 Method

Calculations using the MNDO-PM3 method were performed to elucidate the mechanism of stereoselective base-catalyzed reaction affording exclusively ( Z)-2-alkylidene-4-oxothiazolidine push-pull derivatives from the corresponding α-mercapto esters and activated β-oxonitriles in ethanol as a solvent.

scholarly journals Stereoselective Synthesis of Carbon-Sulfur-Bridged Glycomimetics by Photoinitiated Thiol-Ene Coupling Reactions

2020 ◽  
Vol 21 (2) ◽  
pp. 573 ◽  
Author(s):  
Magdolna Csávás ◽  
Dániel Eszenyi ◽  
Erika Mező ◽  
László Lázár ◽  
Nóra Debreczeni ◽  
...  
Keyword(s):  
Double Bond ◽  
Stereoselective Synthesis ◽  
Uv Light ◽  
Effect Of Temperature ◽  
Exocyclic Double Bond ◽  
Coupling Reactions ◽  
Structural Variations ◽  
Biological Studies ◽  
Broad Array ◽  
Living Organisms

Oligosaccharides and glycoconjugates are abundant in all living organisms, taking part in a multitude of biological processes. The application of natural O-glycosides in biological studies and drug development is limited by their sensitivity to enzymatic hydrolysis. This issue made it necessary to design hydrolytically stable carbohydrate mimetics, where sulfur, carbon, or longer interglycosidic connections comprising two or three atoms replace the glycosidic oxygen. However, the formation of the interglycosidic linkages between the sugar residues in high diastereoslectivity poses a major challenge. Here, we report on stereoselective synthesis of carbon-sulfur-bridged disaccharide mimetics by the free radical addition of carbohydrate thiols onto the exo-cyclic double bond of unsaturated sugars. A systematic study on UV-light initiated radical mediated hydrothiolation reactions of enoses bearing an exocyclic double bond at C1, C2, C3, C4, C5, and C6 positions of the pyranosyl ring with various sugar thiols was performed. The effect of temperature and structural variations of the alkenes and thiols on the efficacy and stereoselectivity of the reactions was systematically studied and optimized. The reactions proceeded with high efficacy and, in most cases, with complete diastereoselectivity producing a broad array of disaccharide mimetics coupling through an equatorially oriented methylensulfide bridge.

scholarly journals Stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene: a general intramolecular Diels–Alder approach to tricyclic sesquiterpenes

1985 ◽  
Vol 63 (4) ◽  
pp. 993-995 ◽  
Author(s):  
Kazimierz Antczak ◽  
John F. Kingston ◽  
Alex G. Fallis
Keyword(s):  
Double Bond ◽  
Methyl Ester ◽  
Total Synthesis ◽  
Ring System ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
Total Syntheses ◽  
Methyl Group ◽  
Secondary Hydroxyl ◽  
Selective Hydrogenolysis

Stereoselective total synthesis of (±)-sinularene and (±)-5-epi-sinularene are described. The sequence employs a "blocked" cyclopentadiene in which the cyclopropane unit also serves as a latent methyl group. Thus intramolecular [4 + 2] cycloaddition of the substituted methyl spiro[2.4]hepta-4,6-dien-1-yl)-2-pentenoate 11 affords 5-benzyloxy-6-isopropyl-8-carbomethoxytetracyclo[5.4.01,7.02,4.02,9]undec-10-ene (12) which after selective hydrogenolysis generates the tricyclo[4.4.01,6.02,8]decane (sinularene) ring system. Removal of the secondary hydroxyl function (Ph3P/CCl4/CH3CN; H2/Pd/C), reduction of the methyl ester (LiAlH4), and introduction of the exocyclic double bond (acetate pyrolysis, 550 °C) completes the synthesis of (±)-sinularene in 14 steps from cyclopentadiene. A parallel series of reactions employing the isopropyl epimer of 12 affords (±)-5-epi-sinularene.

Formation of Dihydroaza-azulanones Possessing Spirocyclic Moieties: [8+2] Type Cycloaddition Reactions of Iminotropones to an Exocyclic Double Bond of 8-Oxoheptafulvene

Heterocycles ◽  
1995 ◽  
Vol 41 (10) ◽  
pp. 2181 ◽  
Author(s):  
Katsuhiro Saito ◽  
Yuka Saito ◽  
Masayuki Tomita ◽  
Hiroshi Taniguchi ◽  
Hirofumi Okabayashi
Keyword(s):  
Double Bond ◽  
Exocyclic Double Bond ◽  
Cycloaddition Reactions

Structurally original oxathioethers macrocycles containing an exocyclic double-bond: synthesis, characterization, reactivity, and coordination

Tetrahedron ◽  
2014 ◽  
Vol 70 (35) ◽  
pp. 5650-5658 ◽  
Author(s):  
Guillaume Carel ◽  
Alina Saponar ◽  
Nathalie Saffon ◽  
Marc Vedrenne ◽  
Stéphane Massou ◽  
...  
Keyword(s):  
Double Bond ◽  
Exocyclic Double Bond
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