- A Synthesis Strategy for the Production of a Macrolactone of Gulmirecin A via a Ni(0)-Mediated Reductive Cyclization Reaction
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A synthesis strategy for the production of a key synthetic intermediate of gulmirecin A was described. The key reaction in the preparation of the 12-membered macrolactone is the Ni(0)-mediated reductive cyclization reaction of ynal using an N-heterocyclic carbene ligand and silane reductant. In addition, the α-selective glycosylation reaction of the macrolactone was performed to demonstrate the synthesis of gulmirecin and disciformycin precursors.
- Ichikawa, Satoshi,Katsuyama, Akira,Kitahata, Shun
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supporting information
(2020/03/30)
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- Stereoselective acetylation of hemicellulosic C5-sugars
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The stereoselective peracetylation of α-D-xylose (1) and α-L-arabinose (4) using a combination of triethylamine and acetic anhydride in the presence or absence of a catalytic amount of dimethylaminopyridine (DMAP) is described. The peracetylated D-xylose and L-arabinose alpha pyranose anomers 2α and 5α are obtained in 97% and 56% yields respectively. The peracetylated D-xylose beta pyranose anomer 2β is obtained in 71% yield through simple modification of the reaction conditions. Details regarding synthesis and isolation optimization studies under different conditions are presented below. The stereoselective peracetylation reactions disclosed here have been used to separate mixtures of D-xylose and L-arabinose as their peracetylated derivatives 2β and 5α in 47% and 42% yields and can provide pure pentoses after deacetylation.
- Herde, Zachary D.,John, Prathap D.,Alvarez-Fonseca, Dania,Satyavolu, Jagannadh,Burns, Christopher T.
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- Two-step synthesis of per-O-acetylfuranoses: Optimization and rationalization
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A simple two-step procedure yielding peracetylated furanoses directly from free aldoses was implemented. Key steps of the method are (i) highly selective formation of per-O-(tert-butyldimethylsilyl)furanoses and (ii) their clean conversion into acetyl ones without isomerization. This approach was easily applied to galactose and structurally related carbohydrates such as arabinose, fucose, methyl galacturonate and N-acetylgalactosamine to give the corresponding peracetylated targets. The success of this procedure relied on the control of at least three parameters: (i) the tautomeric equilibrium of the starting unprotected oses, (ii) the steric hindrance of both targeted furanoses and silylating agent, and finally, (iii) the reactivity of each soft nucleophile during the protecting group interconversion.
- Dureau, Remy,Legentil, Laurent,Daniellou, Richard,Ferrieres, Vincent
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p. 1301 - 1307
(2012/04/04)
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- Synthesis of a dimer of β-(1,4)-l-arabinosyl-(2 S,4 R)-4-hydroxyproline inspired by art v 1, the major allergen of mugwort
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Nα-tert-Butoxycarbonyl-l-trans-4-hydroxyproline allyl ester (Boc-Hyp-OAll) was glycosylated with 2,3,5-tri-O-benzyl-l-arabinose p-cresylthioglycoside in 60% yield with 4:1 β:α stereoselectivity. Deprotection of N- and C-terminii independently gave a prolyl amine and prolyl carboxylate respectively that were coupled under standard conditions with 1-[bis-(dimethylamino)methylene]-1H-1,2,3-triazolo-[4,5,b]-pyridininium hexafluorophosphate 3-oxide (N-HATU) to give the dimer 1 in 46% yield. These results represent the first steps toward the production of homogeneous oligomers to determine the minimal epitope of the Art v 1 allergen.
- Xie, Ning,Taylor, Carol M.
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supporting information; experimental part
p. 4968 - 4971
(2010/12/25)
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- Synthesis of 5-deoxy-β-d-galactofuranosides as tools for the characterization of β-d-galactofuranosidases
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Derivatives of 5-deoxy-β-d-galactofuranose (5-deoxy-α-l-arabino- hexofuranose) have been synthesized starting from d-galacturonic acid. The synthesis of methyl 5-deoxy-α-l-arabino-hexofuranoside (14α) was achieved by an efficient strategy previously optimized, involving a photoinduced electron transfer (PET) deoxygenation. Compound 14α was converted into per-O-acetyl-5-deoxy-α,β-l-arabino-hexofuranoside (16), an activated precursor for glycosylation reactions. The SnCl4-promoted glycosylation of 16 led to 4-nitrophenyl (19α), and 4-methylthiophenyl 5-deoxy-α-l-arabino-hexofuranosides (20α). The oxygenated analog 4-methylphenyl 1-thio-β-d-galactofuranoside (23β) was also prepared. The 5-deoxy galactofuranosides were evaluated as inhibitors or substrates of the exo-β-d-galactofuranosidase from Penicillium fellutanum, showing that the absence of HO-5 drastically diminishes the affinity for the protein.
- Bordoni, Andrea,De Lederkremer, Rosa M.,Marino, Carla
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experimental part
p. 5339 - 5345
(2010/09/05)
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- Studies toward the total synthesis of carba analogue of motif C of M. TB cell wall AG complex
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Herein we describe the synthesis of the carba analogue of motif C of arabinogalactan complex present in M. tuberculosis cell wall. Pd(0) catalyzed allylic alkylation and Fraser-Reid's glycosidation are the two key reactions that were employed for the synthesis of central glycosyl accepter unit and the glycosylation respectively.
- Gurjar, Mukund K.,Reddy, Challa Nageswar,Kalkote, Uttam R.,Chorghade, Mukund S.
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scheme or table
p. 909 - 925
(2010/10/20)
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- Diastereoselective enzymatic preparation of acetylated pentofuranosides carrying free 5-hydroxyl groups
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Methyl 3-O-acetyl-2-deoxy-α-d-ribofuranoside, 1,3-di-O-acetyl-2-deoxy-α-d-ribofuranose and 1,2,3-tri-O-acetyl-α-d-arabinofuranose were diastereoselectively prepared (de = 100%) from anomeric mixtures of the corresponding 5-acetylated compounds through Can
- Gudino, Esteban D.,Iribarren, Adolfo M.,Iglesias, Luis E.
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experimental part
p. 1813 - 1816
(2009/12/26)
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- Vinyl acetate and sodium carbonate as a fast and efficient catalyst for per-O-acetylation of monosaccharides
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Vinyl acetate and sodium carbonate catalysed acetylation of several monosaccharides is an efficient synthesis of per-O-acetylation of carbohydrates and achieve the products in excellent yields and short reaction times. D-Glucose as the substrate in large scale also proceeds in high yield.
- Chen, Li,Zhang, Jianbo,Shi, Chunjuan,Wang, Xiaohu,Zhang, Bo,Tang, Jie
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experimental part
p. 380 - 382
(2009/06/18)
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- On the use of 3,5-O-benzylidene and 3,5-O-(Di-tert-butylsilylene)-2-O- benzylarabinothiofuranosides and their sulfoxides as glycosyl donors for the synthesis of β-arabinofuranosides: Importance of the activation method
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A 2-O-benzyl-3,5-O-benzylidene-α-D-thioarabinofuranoside was obtained by reaction of the corresponding diol with α,α-dibromotoluene under basic conditions. On activation with 1-benzenesulfinyl piperidine, or diphenyl sulfoxide, and trifluoromethanesulfonic anhydride in dichloromethane at -55 °C, reaction with glycosyl acceptors affords anomeric mixtures with little or no selectivity. The analogous 2-O-benzyl-3,5-O-(di-tert-butylsilylene)- α-D-thioarabinofuranoside also showed no significant selectivity under the 1-benzenesulfinyl piperidine or diphenyl sulfoxide conditions. With N-iodosuccinimide and silver trifluoromethanesulfonate the silylene acetal showed moderate to high β-selectivity, independent of the configuration of the starting thioglycoside. High β-selectivity was also obtained with a 2-O-benzyl-3,5-O-(di-tert-butylsilylene)-α-arabinofuranosyl sulfoxide donor on activation with trifluoromethanesulfonic anhydride. The high β-selectivities obtained by the N-iodosuccinimide/silver trifluoromethanesulfonate and sulfoxide methods are consistent with a common intermediate, most likely to be the oxacarbenium ion. The poor selectivity observed on activation of the thioglycosides with the 1-benzenesulfinyl piperidine, or diphenyl sulfoxide, and trifluoromethanesulfonic anhydride methods appears to be the result of the formation of a complex mixture of glycosyl donors, as determined by low-temperature NMR work.
- Crich, David,Pedersen, Christian Marcus,Bowers, Albert A.,Wink, Donald J.
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p. 1553 - 1565
(2007/10/03)
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- The arabinofuranoside method, a convenient substitute of the fucofuranoside method for determining the absolute configuration of the secondary alcohols
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As a simple substitute of the fucofuranoside method, a recently devised technique for determining the absolute configuration of secondary alcohols by 13C NMR, the arabinofuranoside method is proposed. Unlike fucose, the derivatizing agent arabi
- Kobayashi, Masaru
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p. 9365 - 9371
(2007/10/03)
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- A method for obtaining equilibrium tautomeric mixtures of reducing sugars via glycosylamines using nonaqueous media
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Equilibrium tautomeric mixtures of several mono- and disaccharides are obtained in anhydrous form, without the use of water, by reacting the commercially available reducing sugars with ammonia gas in dry methanol, followed by the concentration of the resultant solution to dryness. Mutarotation and hydrolysis of the initially formed glycosylamine in the resultant medium account for the transformation. Equilibrium anomeric mixtures enriched in the β-form of commercially available sugars such as α-D-glucose and α-lactose have not only vastly increased solubility, but are also synthetically valuable as these can be readily converted to the methyl/benzyl/trimethylsilyl ether and other derivatives for further transformations.
- Allavudeen, Sikkander Sulthan,Kuberan, Balagurunathan,Loganathan, Duraikkannu
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p. 965 - 968
(2007/10/03)
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- The influence of boric acid on the acetylation of aldoses: 'One-pot' syntheses of penta-O-acetyl-β-D-glucofuranose and its crystalline propanoyl analogue
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When glucose and boric acid are heated in acetic acid a soluble compound forms from which, with acetic anhydride and catalytic amounts of sulfuric acid, a mixture consisting of >90% of the glucofuranose per-acetates (α : β ratio 1 : 1.8) is obtained in high yield. In the absence of the sulfuric acid partial acetylation takes place and penta-O-acetyl-β-D-glucofuranose (α: β ratio 1 : 52) is obtainable in good yield by removal of boric acid and completion of the esterification by addition of acetic anhydride and pyridine. A new, crystalline glucofuranose, penta-O-propanoyl-β-D-glucofuranose, is obtained in 58% yield in a 'one-pot' procedure using boric acid. The effects of boric acid on the acid-catalysed acetylation of other aldo-hexoses and -pentoses suggest that the synthesis of furanosyl per-esters could be successful with xylose and idose as well as with glucose.
- Furneaux, Richard H.,Rendle, Phillip M.,Sims, Ian M.
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p. 2011 - 2014
(2007/10/03)
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- H-Beta zeolite as an efficient catalyst for per-O-acetylation of mono- and disaccharides
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Among the six different zeolites examined, H-beta is demonstrated to be a highly efficient and selective catalyst for the per-O-acetylation of various mono-and disaccharides and methyl glycosides.
- Bhaskar, Pallooru Muni,Loganathan, Duraikkannu
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p. 129 - 131
(2007/10/03)
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- Per-O-acetylation of sugars catalysed by montmorillonite K-10
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The inexpensive solid acid, montmorillonite K-10, is shown to be an efficient catalyst for the per-O-acetylation of several mono-, di- and trisaccharides. The pyranose forms accounted for 75- 100% of the acetylated products.
- Bhaskar, Pallooru Muni,Loganathan, Duraikkannu
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p. 2215 - 2218
(2007/10/03)
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