A stereoselective synthesis of sucrose. Part II. Theoretical and chemical considerations

1979 ◽  
Vol 57 (6) ◽  
pp. 645-652 ◽  
Author(s):  
Bert Fraser-Reid ◽  
David Erle Iley
Keyword(s):  
Melting Point ◽  
Stereoselective Synthesis ◽  
Primary Alcohol ◽  
Hydroxyl Group ◽  
Borohydride Reduction ◽  
Conjugated Diene

Under the agency of an iodonium ion, the tertiary anomeric hydroxyl of tetraacetyl fructofuranose adds stereoselectively in a 1,4 sense, to a pyranoid 4,6-O-benzylidenated conjugated diene receptor. The resulting disaccharide, isolated in 45% yield, is an hex-2-enopyranoside possessing an allylic primary iodide which can be oxidised to an aldehyde either directly or after hydrolysis to the allylic primary alcohol. The aldehyde is decarbonylated and the unsubstituted hex-2-enopyranoside formed undergoes hydroxylation giving exclusively the manno-diol. After protecting the equatorial hydroxyl as the benzoate ester, the axial 2-hydroxyl group is inverted via oxidation followed by borohydride reduction. Acetylation gives the known 4,6-O-benzylidene hexaacetyl derivative of sucrose, which is identified by mixture melting point.

Synthesis of Three Novel Aromatic Biazomethine Liquid- Crystalline Epoxy Resins and Curing Reaction with Aromatic Diamine

2011 ◽  
Vol 216 ◽  
pp. 34-38
Author(s):  
Jun Gang Gao ◽  
Xiao Na Zhang ◽  
Yong Gang Du
Keyword(s):  
Melting Point ◽  
Epoxy Resins ◽  
Liquid Crystalline ◽  
Diphenyl Ether ◽  
Hydroxyl Group ◽  
Aromatic Diamine ◽  
Curing Reaction ◽  
Ozawa Equation ◽  
Liquid Crystalline Epoxy ◽  
Clearing Temperature

Three class of novel liquid crystalline epoxy resins containing azomething groups: N,N’-Bis[4-(2,3-epoxypropoxy)benzylidene]-4,4-diamino-diphenyl ether (p-BEPBDDE), N,N’-Bis[4-(2,3-epoxypropoxy)benzylidene]-4,4-diamino-diphenyl methane (p-BEPBDDM) and N,N’-Bis[(4-(2,3-epoxypropoxy)-benzyliden)-1,4- phenylene diamine] (p-BEPBPD) were synthesized and characterized. The results show that p-BEBDDE and p-BEBDDM belong to smectic texture and melting point is 239.5 and 178 oC, respectively. The p-BEPBD is nematic texture between its melting temperature (Tm) of 192 oC and clearing temperature (Ti) of 238 oC. The curing reaction can be described by Ozawa equation, and the alcohol-hydroxyl group can accelerate the curing reaction and decrease Ea in DSC experiment.

scholarly journals Isolasi dan Identifikasi Senyawa Metabolit Sekunder Ekstrak Aseton Daun Tumbuhan Tembelekan (Lantana camara Linn.)

2019 ◽  
Vol 20 (2) ◽  
pp. 179
Author(s):  
Rosni Kotala ◽  
Diana Eka Pratiwi ◽  
Ramdani Ramdani
Keyword(s):  
Melting Point ◽  
Lantana Camara ◽  
Wave Number ◽  
Hydroxyl Group ◽  
Secondary Alcohols ◽  
Exploratory Research ◽  
South Sulawesi ◽  
Point Test ◽  
Acetone Fractionation ◽  
Spectrum Data

ABSTRAK Penelitian ini adalah penelitian eksplorasi yang bertujuan untuk mengisolasi dan mengidentifikasi senyawa metabolit sekunder dari ekstrak aseton daun tumbuhan tembelekan (Lantana camara Linn.). Daun tumbuhan ini diperoleh dari Kabupaten Wajo, Sulawesi Selatan. Penelitian dilakukan melalui beberapa tahap yaitu preparasi sampel, maserasi dengan aseton, fraksinasi, pemurnian, dan identifikasi. Isolat yang diperoleh berbentuk serbuk berwarna putih yang terdekomposisi pada suhu 222 0C dan uji pereaksi menunjukan hasil positif pada pereaksi Lieberman- Buchard. Data dari hasil Spektrum FTIR menunjukkan pada bilangan gelombang 3126.61 cm-1 mengandung gugus hidroksil (OH), alkil (CH2 danCH3)padabilangangelombang2956,80cm-1 ,C-Oalkoholsekunder pada bilangan gelombang 1039.63 cm-1dan alkena (C=C) tak terkonjugasi pada bilanagan gelombang 1678,07 cm-1. Berdasarkan uji titik leleh, uji pereaksi serta data spektrum FTIR isolat diduga senyawa steroid yang termasuk golongan sterol (steroid alkohol). Kata kunci : Lantana camara Linn., Isolasi, Aseton, Sterol ABSTRACT This exploratory research aimed to isolate and identificate the secondary metabolite compound in aceton extract of tembelekan leaves (Lantana camara Linn.). Samples were obtained from Wajo regency, South Sulawesi. This research was conducted in several steps; preparation, maceration with acetone, fractionation, purification, and identification. The result obtained pure isolate form white powder, melting point of 222 0C and reagent test showed positive of Burchard Lieberman. Data spectrum of FTIR showed wave number (cm-1) of 3126.61 cm-1 as a hydroxyl group (OH), alkyl (CH2 and CH3) at wave number 2956.80 cm-1, CO secondary alcohols at wave number 1039.63 cm-1 and alkene (C = C) unconjugated at wave number of 1678.07 cm-1. Based on the melting point test, reagent test and FTIR spectrum data showed that the isolate steroid compound as sterol group (alcohol steroid). Keywords : Lantana camara Linn., Isolation, Acetone, Sterols

scholarly journals Stereoselective Synthesis of Highly-Congested Tetralin-Fused Spirooxindoles with Hydroxyl Group: Net Oxygen Atom Induced Hydride Shift/cyclization Process.

2021 ◽  
Author(s):  
Dan Sakai ◽  
mizuki machida ◽  
Keiji Mori
Keyword(s):  
Reaction Mechanism ◽  
Nitrogen Atom ◽  
Oxygen Atom ◽  
Stereoselective Synthesis ◽  
Hydroxyl Group ◽  
Target Structure ◽  
Hydride Shift ◽  
Cyclization Process ◽  
Stereogenic Centers

Highly stereoselective synthesis of tetralin-fused spirooxindoles with two contiguous stereogenic centers. In the present reaction, not only [1,5]-hydride shift/cyclization process, but also replacemnt of nitrogen atom to oxygen atom ocurred smoothly to give target structure with hydroxy grop in good chemical yields with good to excellent diastereoselectivities (up to d.r. = >20:1). Investigation of the reaction mechanism suggested that this “atom-replacement” event ocurred via the iminium cation intermediates.

scholarly journals An Efficient Synthesis of Tetrodotoxin

2021 ◽  
Author(s):  
David Konrad ◽  
Peter Ruehmann ◽  
Hiroyasu Ando ◽  
Belinda Hetzler ◽  
Bryan Matsuura ◽  
...  
Keyword(s):  
Tertiary Amine ◽  
Stereoselective Synthesis ◽  
Primary Alcohol ◽  
Biologically Active ◽  
Dipolar Cycloaddition ◽  
Protecting Group ◽  
Efficient Synthesis ◽  
Ready Access ◽  
Biologically Active Derivatives ◽  
Glucose Derivative

Tetrodotoxin (TTX) is an indispensable probe in neuroscience, a biosynthetic and ecological enigma, and one of the most celebrated targets of synthetic chemistry. Here, we present a stereoselective synthesis of TTX that proceeds in 22 steps starting from a readily available glucose derivative. The central cyclohexane ring of TTX and its α-tertiary amine moiety was established via the intramolecular 1,3-dipolar cycloaddition of a nitrile oxide, followed by alkynyl addition to the resultant isoxazoline. After some carefully chosen protecting group manipulations, a ruthenium-catalyzed hydroxylactonization set the stage for the formation of its dioxa-adamantane core. Installation of the guanidine, oxidation of a primary alcohol, and late-stage epimerization of the resultant aldehyde gave a mixture of TTX and anhydro TTX. Our synthesis represents one of the most effective of TTX reported to date and could give ready access to biologically active derivatives.

Chiral transformations of D-ribose to 2(S)-amino-2-[2,5-dihydro-5(R)-methylfuran-2(R)-yl]ethanoic acid, a diastereomer of the antibiotic (+)-furanomycin

1983 ◽  
Vol 61 (2) ◽  
pp. 317-322 ◽  
Author(s):  
Morris J. Robins ◽  
J. M. Robert Parker
Keyword(s):  
Amino Acid ◽  
Primary Alcohol ◽  
Reductive Elimination ◽  
Chain Extension ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Type Synthesis ◽  
Ethanoic Acid ◽  
Concomitant Reduction

The chain-extended 2-(2,3-O-isopropylidene-β-D-ribofuranosyl)-1,3-diphenylimidazolidine derivative (3a) was prepared by a known sequence from D-ribose. Benzylation of the primary alcohol function of 3a, deprotection of the masked aldehyde, chain extension using a modified Strecker-type synthesis, and acetylation of the resulting epimeric 2-hydroxyl groups gave the appropriately blocked seven-carbon 3,6-anhydro compounds (5a, b). The primary alcohol function was deprotected and then removed by mesylation, iodide replacement, and hydrogenolysis. The 2-hydroxyl group was deprotected, mesylated, and replaced by azide. Methanolysis of the amide and isopropylidene groups gave the α-azido ester diols (13a, b). Treatment of 13a with thiocarbonyldiimidazole followed by the Corey–Winter reaction with trimethylphosphite effected concomitant reduction of the azide function and reductive elimination of the cyclic thionocarbonate group. Saponification of the ester intermediate gave the target α-amino acid, 2(S)-amino-2-[2,5-dihydro-5(R)-methylfuran-2(R)-yl]ethanoic acid (1). Comparison of the properties of 1 and (+)-furanomycin confirmed the necessity of revision of stereochemistry for the antibiotic.

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