Sweet Poisons: Synthetic Strategies towards Tutin Glycosides

2017 ◽  
Vol 70 (3) ◽  
pp. 301 ◽  
Author(s):  
Duong Nhu ◽  
Lesley Larsen ◽  
Nigel B. Perry ◽  
David S. Larsen ◽  
Bill C. Hawkins
Keyword(s):  
Double Bond ◽  
Major Product ◽  
Protecting Groups ◽  
Benzyl Ether ◽  
Reaction Conditions ◽  
Double Bond Migration ◽  
Epoxide Opening ◽  
Glycosylation Reaction ◽  
Cationic Palladium

The polycyclic, polyoxygenated picrotoxane tutin was subjected to various glycosylation reaction conditions in an effort to synthesise β-linked tutin glycosides, recently found in toxic honeys. Cationic palladium-mediated glycosylation of tutin was successful; however, the α-linked tutin tetrabenzyl glucoside was obtained as the major product (5 : 1, α : β). Hydrogenolysis of the benzyl ether protecting groups resulted in concomitant tutin double-bond migration. Epoxide opening and rearrangement were observed upon acetylation of the tutin glucoside.

Catalytic Hydrogenation with Amorphous and Crystalline Pd8 0Si2 0

1981 ◽  
Vol 8 ◽  
Author(s):  
Bill C. Giessen ◽  
Sabri S. Mahmoud ◽  
David A. Forsyth ◽  
Markus Hediger
Keyword(s):  
Double Bond ◽  
Catalytic Hydrogenation ◽  
Metallic Glasses ◽  
Hydrogen Deuterium Exchange ◽  
Reaction Conditions ◽  
Crystalline Phases ◽  
Hydrogenation Catalysts ◽  
Double Bond Migration ◽  
Hydrogenation Reactions ◽  
Hydrogen Deuterium

ABSTRACTSeveral metallic glasses in the form of ribbons were screened for activity as hydrogenation catalysts. Pd80Si20 and (Ni50Fe50)80B20 showed activity in reducing cyclohexene. Pd 80 Si20 was further examined for differences between the glassy and crystalline phases in the selectivity shown during hydrogenation reactions of n-hexenes, phenylethyne, α-pinene, and cyclododecene. No significant differences were found for catalytic selectivity in regard to cis-trans isomerization, double bond migration, and stereochemistry of addition under the reaction conditions used. Minor differences were observed in hydrogen-deuterium exchange.

Reactions directed towards the synthesis of 5-(β-hydroxyethyl)-2-isopropylcyclohexanone

1978 ◽  
Vol 31 (7) ◽  
pp. 1629 ◽  
Author(s):  
R Murphy ◽  
R Prager
Keyword(s):  
Double Bond ◽  
Partial Migration ◽  
Reaction Conditions ◽  
Double Bond Migration ◽  
Bond Rearrangement

Reduction of perillaldehyde by lithium in ammonia gives products the structures of which depend on reaction conditions. Shisool (p-menth-8- en-7-ol) undergoes double-bond migration in the presence of acids. The corresponding aldehyde, with dimethylsulfonium methylide, forms an oxiran which is comparatively unreactive, double-bond rearrangement or reduction accompanying the opening of the oxiran. The conversion of shisool into 5-(β-hydroxyethyl)-2-isopropylcyclohexanone was frustrated by only partial migration of the double bond.

Utility of the Cleavage of Nitrosamides for the Preparation of Chiral Acids after Chromatographic Separation of their Diastereomeric Amides

1977 ◽  
Vol 32 (1) ◽  
pp. 98-104 ◽  
Author(s):  
Franz P. Schmidtchen ◽  
Peter Rauschenbach ◽  
Helmut Simon
Keyword(s):  
Double Bond ◽  
Carboxylic Acids ◽  
Chromatographic Separation ◽  
Optical Resolution ◽  
Double Bonds ◽  
Reaction Conditions ◽  
Double Bond Migration ◽  
Enantiomerically Pure ◽  
Amide Derivatives ◽  
Derivatives Of

A method for optical resolution of chiral acids is described. It consists of the conversion of racemic acids to diastereomeric amides, their chromatographic separation and subsequent deamidation via the nitrosamide route. Reaction conditions for cleavage of amide derivatives of phenylalanine and methylbenzylamine are given. No or only negligible racemization of carboxylic acids, chiral in α-position takes place under those conditions. The extent of Ε,Ζ-isomerization of double bonds is very small, as is the extent of double bond migration from the Δ3-position into conjugation with the carboxyl function. Enantiomerically pure R- or S[2-3H]2-methylbutanoic acid and (-)methyl-3(p-chlorophenyl)-2-chloropropionate (Bidisin®) were prepared by this procedure.

Visible Light-Mediated Oxidative Debenzylation

2020 ◽  
Author(s):  
Cristian Cavedon ◽  
Eric T. Sletten ◽  
Amiera Madani ◽  
Olaf Niemeyer ◽  
Peter H. Seeberger ◽  
...  
Keyword(s):  
Reaction Time ◽  
Visible Light ◽  
Functional Groups ◽  
Continuous Flow ◽  
Protecting Groups ◽  
Benzyl Ether ◽  
Complex Molecules ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Harsh Conditions

Protecting groups are key in the synthesis of complex molecules such as carbohydrates to distinguish functional groups of similar reactivity. The harsh conditions required to cleave stable benzyl ether protective groups are not compatible with many other protective and functional groups. The mild, visible light-mediated debenzylation disclosed here renders benzyl ethers orthogonal protective groups. Key to success is the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as stoichiometric or catalytic photooxidant such that benzyl ethers can be cleaved in the presence of azides, alkenes, and alkynes. The reaction time for this transformation can be reduced from hours to minutes in continuous flow. <br>

A Facile, Efficient and Selective Deprotection of P - Methoxy Benzyl Ethers Using Zinc (II) Trifluoromethanesulfonate

2019 ◽  
Vol 16 (12) ◽  
pp. 955-958
Author(s):  
Reddymasu Sireesha ◽  
Reddymasu Sreenivasulu ◽  
Choragudi Chandrasekhar ◽  
Mannam Subba Rao
Keyword(s):  
Room Temperature ◽  
Protecting Groups ◽  
Side Reactions ◽  
Reaction Conditions ◽  
Acid Sensitivity ◽  
Time Period ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Last Stage ◽  
Zinc Triflate

: Deprotection is significant and conducted over mild reaction conditions, in order to restrict any more side reactions with sensitive functional groups as well as racemization or epimerization of stereo center because the protective groups are often cleaved at last stage in the synthesis. P - Methoxy benzyl (PMB) ether appears unique due to its easy introduction and removal than the other benzyl ether protecting groups. A facile, efficient and highly selective cleavage of P - methoxy benzyl ethers was reported by using 20 mole% Zinc (II) Trifluoromethanesulfonate at room temperature in acetonitrile solvent over 15-120 min. time period. To study the generality of this methodology, several PMB ethers were prepared from a variety of substrates having different protecting groups and subjected to deprotection of PMB ethers using Zn(OTf)2 in acetonitrile. In this methodology, zinc triflate cleaves only PMB ethers without affecting acid sensitivity, base sensitivity and also chiral epoxide groups.

One-pot Synthesis of Pyrazolone Sulfones by Iodine-catalyzed Sulfenylation of Pyrazolones with Aryl Sulfonyl Hydrazides Followed by Oxidation in Water

2018 ◽  
Vol 15 (3) ◽  
pp. 380-387
Author(s):  
Xia Zhao ◽  
Xiaoyu Lu ◽  
Lipeng Zhang ◽  
Tianjiao Li ◽  
Kui Lu
Keyword(s):  
Double Bond ◽  
Efficient Method ◽  
Room Temperature ◽  
Sulfonyl Chloride ◽  
Antibacterial Activities ◽  
Oxidation Reactions ◽  
Reaction Conditions ◽  
One Pot ◽  
X Ray ◽  
Amide Form

Aim and Objective: Pyrazolone sulfones have been reported to exhibit herbicidal and antibacterial activities. In spite of their good bioactivities, only a few methods have been developed to prepare pyrazolone sulfones. However, the substrate scope of these methods is limited. Moreover, the direct sulfonylation of pyrazolone by aryl sulfonyl chloride failed to give pyrazolone sulfones. Thus, developing a more efficient method to synthesize pyrazolone sulfones is very important. Materials and Method: Pyrazolone, aryl sulphonyl hydrazide, iodine, p-toluenesulphonic acid and water were mixed in a sealed tube, which was heated to 100°C for 12 hours. The mixture was cooled to 0°C and m-CPBA was added in batches. The mixture was allowed to stir for 30 min at room temperature. The crude product was purified by silica gel column chromatography to afford sulfuryl pyrazolone. Results: In all cases, the sulfenylation products were formed smoothly under the optimized reaction conditions, and were then oxidized to the corresponding sulfones in good yields by 3-chloroperoxybenzoic acid (m-CPBA) in water. Single crystal X-ray analysis of pyrazolone sulfone 4aa showed that the major tautomer of pyrazolone sulfones was the amide form instead of the enol form observed for pyrazolone thioethers. Moreover, the C=N double bond isomerized to form an α,β-unsaturated C=C double bond. Conclusion: An efficient method to synthesize pyrazolone thioethers by iodine-catalyzed sulfenylation of pyrazolones with aryl sulfonyl hydrazides in water was developed. Moreover, this method was employed to synthesize pyrazolone sulfones in one-pot by subsequent sulfenylation and oxidation reactions.

Some Analogs of 4-(2',4'-Difluorobiphenyl-4-yl)-2-methyl-4-oxobutanoic Acid: Synthesis and Antiinflammatory Activity

1995 ◽  
Vol 60 (6) ◽  
pp. 1026-1033 ◽  
Author(s):  
Miroslav Kuchař ◽  
Václav Vosátka ◽  
Marie Poppová ◽  
Eva Knězová ◽  
Vladimíra Panajotovová ◽  
...  
Keyword(s):  
Double Bond ◽  
Antiinflammatory Activity ◽  
Acid Synthesis ◽  
Reaction Conditions ◽  
Methyl Group ◽  
Oxobutanoic Acid

Analogs of 4-(2',4'-difluorobiphenyl-4-yl)-2-methyl-4-oxobutanoic acid (I, flobufen), containing a double bond (II, IV, V, VII, VIII) or a methyl group in position 3 (VI) were prepared. Their antiinflammatory activity was evaluated and compared with that of flobufen. None of the mentioned analogs reached the activity of the standard. Isomerization of the unsaturated derivatives is connected with a shift of the double bond, Z-E transformation or lactonization. Reaction conditions and spectra of the compounds prepared are described.

Synthesis of sp3-Enriched β-Fluoro Sulfonyl Chlorides

Synthesis ◽  
2020 ◽  
Author(s):  
Oleksandr O. Grygorenko ◽  
Rustam Gurbanov ◽  
Andriy Sokolov ◽  
Sergey Golovach ◽  
Kostiantyn Melnykov ◽  
...  
Keyword(s):  
Drug Discovery ◽  
Double Bond ◽  
Building Blocks ◽  
Protecting Groups ◽  
Sulfonyl Chlorides ◽  
Wide Range ◽  
Cyclic Compounds

AbstractA three-step approach to the synthesis of sp3-enriched β-fluoro sulfonyl chlorides starting from alkenes is reported. The method was successfully applied to a wide range of acyclic and cyclic substrates, bearing either an exocyclic or an endocyclic double bond. The procedure worked with a wide range of substrates and tolerated a number of functional and protecting groups. Moreover, the target cyclic compounds were obtained as single cis diastereomers on a multigram scale. The title compounds are promising building blocks for drug discovery that can be used to obtain sp3-enriched β-fluoro and α,β-unsaturated sulfonamides.

Double bond isomerization of ethyl linoleate and vegetable oils to conjugated derivatives over an LDH supported ruthenium catalyst

RSC Advances ◽  
2015 ◽  
Vol 5 (45) ◽  
pp. 36075-36082 ◽  
Author(s):  
Sivashunmugam Sankaranarayanan ◽  
Gobi Selvam ◽  
Kannan Srinivasan
Keyword(s):  
Double Bond ◽  
Vegetable Oils ◽  
Ethyl Linoleate ◽  
Ruthenium Catalyst ◽  
Reaction Conditions ◽  
Double Bond Isomerization

Isomerization of ethyl linoleate and vegetable oils to conjugated derivatives is achieved over an MgAl-LDH supported ruthenium catalyst under mild reaction conditions.

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