Syntheses of Methyl 2,3-di-O-Glycyl-α-D-glucopyranoside and 4,6-di-O-Glycyl-2,3-di-O-methyl-α-D-glucopyranoside,and Removal of Aminoacyl Groups from Sugar Moieties

Abstract

To confirm the potential usefulness of amino acid residues as protecting groups for sugar hydroxyls, methyl 2,3-di-O-glycyl-α-D-glucopyranoside (5) and methyl 4,6-di-O-glycyl-2,3-di-O-methyl-α-D-gluco-pyranoside (7) were synthesized as reference compounds. Conditions were then established for the removal of these aminoacyl groups from the sugar molecules. The reference compounds were easily prepared by condensation of methyl α-D-glucopyranoside derivatives with N-protected glycine in the presence of dicyclohexyl-carbodiimide (DCC). The aminoacyl groups were removed by alkaline treatment, as were conventional acyl groups and also with ease by enzymatic hydrolysis using Pronase E. Conventional ester and ether protecting groups are not removed by such enzymatic treatment. Removal of aminoacyl group from sugar moieties on a practical scale is also described.     

An Entry to the Optically Pure β-Lactam Skeleton Based on 1,3-Dipolar Cycloaddition of Nitrones to 4,6-Di-O-Acetyl-2,3-Dideoxy-D-Threo-Hex-2-Enono-1,5-Lactone

Abstract

Saturated lactone 8, easily available by 1,3-dipolar cycloaddition of nitrone 4 to unsaturated lactone 7 was transformed into the β-lactam 22having a polyol side chain at the C-3 position of the azetidinone ring. The same sequence of reactions, when applied to 9 and 10 failed to give the respective β-lactams owing to the removal of the nitrogen atoms from those molecules.     

Oxidation of L-sorbose and 2,3;4,6-di-O-isopropylidene-α-L-sorbose over supported platinum and palladium catalysts

Oxidation of L-sorbose and 2,3;4,6-di-O-isopropylidene--L-sorbose by oxygen (air) has been studied over supported Pt and Pd catalysts. The results indicate that the activity and stability of these catalysts are greatly dependent on their composition and preparation conditions.

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L- 2,3;4,6--O---L- () . , .

     

Improved One-pot Synthesis of 4,6-Dihydroxyisophthalic Acid and 2,3-Dihydroxyterephthalic Acid

An improved method for the large-scale preparation of 4,6-dihydroxyisophthalic acid and 2,3-dihydroxyterephthalic acid has been developed.Compared to the previous procedures,this new process-requires much lower CO2 pressure of 0.3 Mpa and shorter reaction time.thus providing a convenient access for large-scale synthesis.The yield is high （93% and 65%,respectively）, and the oxidation of phenol is nearly inhibited,neither decolorization nor further chromatographic purification is required.     

Some Aspects of the Reaction of Methyl 4,6-O-benzylidene-α-D-glucopyranoside 2,3-Carbonate with 1-Dodecanol: Novel Non-Ionic Surfactants

Abstract

The reaction of methyl 4, 6-0-benzylidene-α-D-glucopyranoside 2, 3-cyclic carbonate (2) with 1-dodecanol in the presence of a catalytic amount of triethylamine to yield the 2-O-and the 3-O-alkoxycarbonyl esters 5 and 6 is described. Catalytic hydrogenation of 5 and 6 gave the deprotected mono-esters 3 and 4 which are of interest as potential non-ionic surfactants. The corresponding ethoxycarbonyl esters 7 and 8 were also prepared and their possible role as intermediates in the formation of 2 is discussed.     

STUDY ON CATIONIC RING-OPENING COPOLYMERIZATION OF 1,4-ANHYDRO-2,3-DI-O-BENZYL-α-D-RIBOPYRANOSE WITH 1,4-ANHYDRO-2,3-O-ISOPROPYLIDENE-α-D-RIBOPYRANOSE

Cationic ring-opening copolymerization of 1, 4-anhydro-2, 3-O-isopropylidene-α-D-ribo-pyranose (AIRP) with 1,4-anhydro-2,3-di-O-benzyl-α-D-ribopyranose (ADBR) preparedfrom D-ribose was studied. Copolymerization using SbCl_5 or BF_3 OEt_2 as catalyst atlow temperature gave stereoregular (1→4)β-D-ribofuranan (C-1 and C-4 ring cleavagesee Scheme 1) or (1→5) α-D-ribofuranan (C-1 and C-5 ring cleavage) respectively. Theeffects of catalysts, reaction time and temperatures on yield and stereoregularity of the ob-tained polymers were studied. Polymers were characterized by molecular weight, ~1HNMR,~(13)CNMR and optical rotation.     

α-Nitro carbonyl compounds in the synthesis of 2,3-dihydrofurans

A new method for the synthesis of 2,3-dihydrofurans from readily available starting enones and α-nitro carbonyl compounds has been developed. This protocol can provide a novel and effective methodology for the preparation of 2,3-dihydrofurans in a stereoselective fashion. With 1,4-dien-3-ones, 2,3-dihydrofurans and cyclohexenecarboxylates were produced and high chemoselectivity was observed in different solvents.     

新型4,6-脱水-α-D-吡喃型半乳糖衍生物的合成

以甲基-2,3,4,6-四-O-苄基-α-D-吡喃型半乳糖为起始原料,通过对1-位和2-位进行结构修饰,6-位选择性脱除苄基后,再引入保护基Ms(或Ts)制得3,4-二-O-苄基-6-磺酰基(或对甲苯基磺酰基)-α-D-吡喃型半乳糖衍生物(2a~2f);在AcOK/DMSO体系中于80℃反应24 h,2发生分子内亲核取代反应合成了一系列新型的4,6-脱水-α-D-吡喃型半乳糖衍生物,产率78%~88%,其结构经1H NMR,13C NMR和ESI-HR-MS表征。     

Oxidation of Methyl 4,6-O-Isopropylidene-α-d-glucopyranoside as a Model Compound for Starch

Abstract

The oxidation of methyl 4,6-O-isopropylidene-α-d-glucopyranoside (1) via various routes to the dicarboxylate 2 is described. This reaction is used as a model for the oxidation of starch to dicarboxylic starch, a material with very promising properties as a cobuilder in detergents. The best oxidant found for C₂-C₃ cleavage was RuO₄, prepared in situ by oxidation of a catalytic amount of Ru^III with NaOCl.     

α—甲基丙烯酸2,3—环氧丙基酯的选择性阴离子聚合

通过对α－甲基丙烯酸２，３－环氧丙基酯双键的选择性阴离子聚合的研究发现：在较低下（＜－４０℃）聚合中的副反应主要发生在引发阶段，以引发剂与单体中环氧基的副反应为主；当温度较高时（＞－２０℃）则易出现交现象而难以进行双键的选择性聚合，ＧＰＣ、ＨＮＭＲ及ＦＴＩＲ鉴定表明，在较低温度下１，１＇－二苯基己基锂作引发剂可合成每个重复单元上均定量带有的环氧基的单分散（Ｍｗ／Ｍｎ＜１．１０）官能性聚合物，该聚合     

Luminescent Tetranuclear Copper（l） Phenylacetylide Complex with Cyclohexyl Isocyanide

Depolymerizing polymeric phenylacetylide copper(I)[Cu(C≡CPh)]n with cyclohexyl isocyanide (CNCy) gave the tetranuclear copper(I) complex Cu4(CNCy)4(μ-η^1-C≡CPh)2(μ3-η^1,η^2,η^2C≡CPh)2. The crystal structure was determined X-ray crystallography. The phenylacetylide adopts μ-η^1 and μ3-η^1,η^2,η^2bonding modes. The complexshows intense luminescence in solidstate.     

Luminescent Tetranuclear Copper（I） Phenylacetylide Complex with Cyclohexyl Isocyanide

1INTRODUCTIONThechemistryofmetalalkynylcomplexeshasattractedmuchattentioninrecentyearsduetothespecificinterestinstructuraltopologyandopticalproperties[1～6].Ithasbeendemonstratedthatoneofthefeasiblestrategiestoattainoligomericmetalalky-nylcomplexesistodepolymerizepolymericspeciesofmetalalkynylsbyusingorganicligandssuchasphosphines[7～11]andisocyanides[12～14].Insomecases,simplemetal-containingcomponentsarealsoavail-abletodepolymerizethepolymericmetalalkynyl,formingalkynyl-bridgedheterometa…     

Stereoselective synthesis of 2,3-diamino-2,3-dideoxy-β-D-mannopyranosyl uronates

With the aim to find an efficient synthetic procedure for the construction of 2,3-diamino-2,3-dideoxy-β-D-mannuronic acids, we evaluated three mannosyl donors: (S)-phenyl 4,6-di-O-acetyl-2,3-diazido mannopyranoside, (S)-phenyl 2,3-diazido-4,6-O-benzylidene mannopyranoside, and (S)-phenyl 2,3-diazido mannopyranosyl methyl uronate. The first two mannosylating agents are rather unselective or slightly α-selective in their condensation with three different acceptors. The mannuronic acid donor on the other hand reliably provides the desired β-mannosidic linkage. A mechanistic rationale is put forward to account for the different behavior of the three donor types. Suitably protected 2,3-diazido mannuronic acids were employed to construct the all-cis-linked tetrasaccharide repeating unit of the capsular polysaccharide of Bacillus stearothermophilus , featuring two 2,3-diacetamido-2,3-dideoxy-β-D-mannuronic acids.     

Fragmentation processes in phthalimide- and pyridine-2,3-dicarboimidoalkyl-α-diazoketones under resonant electron capture

Resonant electron capture (REC) mass spectra of phthalimide- and pyridine-2,3-dicarboimidoalkyl-α-diazoketones have been investigated. Based on calculations using the Hartree–Fock method and density functional theory with the B3LYP functional the structure of the negative ions (NIs) [M–N₂]^? and [M–N₂–C₃H₃RO]^? as well as the reactions leading to their formation have been proposed.     

AN ALTERNATE SYNTHESIS OF 4,6-DIHYDROXYQUINAZOLINE

ＡＮＡＬＴＥＲＮＡＴＥＳＹＮＴＨＥＳＩＳＯＦ４，６－ＤＩＨＹＤＲＯＸＹＱＵＩＮＡＺＯＬＩＮＥ￥ＹｉＱａｎｇＺＨＵ；ＨｕｉＴｏｎｇＴＡＮＧ；ａｎｄＰａｎｇＺＨＡＮＧ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＰｅｎｉｎｇＵｎｉｖｅｒｓｉｔｙ，Ｂｅｉｊ...     

On the relation between the solvent parameters and the physical properties of methyl-4,6-O-benzylidene-α-d-glucopyranoside organogels

This paper reports the mechanisms of gel formation, the thermal properties and the microstructures of the networks of the gels composed of methyl-4,6-O-benzylidene-α-d-glucopyranoside and selected organic solvents: p-xylene, benzene, toluene, diphenyl ether and tetraethoxysilane. The Fourier transform infrared measurements together with simulation spectra, the air bath method and Polarized Optical Microscopy were employed in our studies. The experimental data show that the solvent has an influence on the microstructure of the gel network but there is no predictable influence of the solvent polarity on the shape of the formed gelator aggregates and correspondingly on the fibrous assemblies as revealed by the different microstructure of the gel network. Independently of the solvent polarity, the studied gelator, like other methyl-4,6-O-benzylidene derivatives of monosaccharides, formed gels through the formation of a hydrogen-bond network. The solvent parameters, such as the dielectric constant, Hildebrand solubility parameter, the polarity scale E_T and the Kamlet–Taft parameters were considered to quantify solvent effects on the gelation. The conclusions about the correlations are of interest but only to this particular sugar based gels.     

Synthesis of Cyclohexyl and Isopropyl Ketones from Benzimidazole Methiodide Salt and Grignard Reagents

The reaction of 2-alkyl-l, 3-dimethylbenzimidazolinm salts with Grignard reagents gave addition products which were hy-drelyzed to give ketones. A new method for the preparation of cyclohexyl ketones and isopropyl ketones is provided.     

Synthesis of methyl 4,6-O-benzylidene-2,3-dideoxy-5-thio-β-dl-threo-hex-2-enopyranoside via hetero-Diels-Alder reaction and unusual stabilities of 1,5-anhydro-4,6-O-benzylidene 2,3-dideoxy-5-thio-dl-threo-hex-2-enitol

The title compound was prepared via hetero-Diels-Alder reaction of 1-acetoxy-1,3-butadiene and thioaldehyde, followed by Pummerer rearrangement. Different from the corresponding sugar and 5a-carba sugar, C-inside isomer of 1,5-anhydro-4,6-O-benzylidene-2,3-dideoxy-5-thio-dl-thero-hex-2-enitol was found to be thermodynamically more stable than the corresponding O-inside one and these thermodynamic stabilities were corroborated by ab initio calculations.     

Synthesis,Thermal Properties,and Radiolysis of Poly(Cyclohexyl α-Chloroacrylate)

Cyclohexyl α-chloroacrylate (CCA) was polymerized by radical anionic and γ-radiation initiation. The anionic polymerization of cyclohexyl α-chloroacrylate gave moderately isotactic polymer in toluene and syndiotactic-rich polymer in THF. Poly(cyclohexyl α-chloroacrylate) (PCCA) was found to undergo two-stage weight loss in thermogravimetric analysis, and the first-stage weight loss was attributed to the lactonization reaction. PCCA degraded under γ-radiation, and the radiation yields of crosslinking and scission, G _x and G _s, were 0.6 and 3.8, respectively.