Terminal Deoxy Hydroxyamino Sugars

Abstract

Reduction of sugar aldoximes gave in good yield the corresponding terminal deoxy hydroxyamino sugars. These compounds were found to be reasonably stable (they could be kept for some weeks at 4° C). On standing in the air, these compounds in solution were spontaneously oxidized to the corresponding nitroxide free radicals whose ESR spectra gave useful structural information.     

A Novel Route for the Synthesis of Deoxy Fluoro Sugars and Nucleosides

The reaction of (diethylamino)sulfur trifluoride (DAST) with methyl 5-O-benzoyl-β-D -xylofuranoside ( 1 ) followed by column chromatography afforded the riboside 2 (62%) and the ribo-epoxide 3 (18%) (Scheme 1). Under similar reaction conditions, the α-D -anomer 4 gave the riboside 5 and the difluoride 6 in 60 and 9% yield, respectively. Treatment of the β-D -xyloside 10 with DAST gave, after chromatographic purification, the riboside 11 as the principal product (48%; Scheme 2). These results suggest that the C(3)−O−SF₂NEt₂ derivatives were initially formed in the case of the xylosides studied. The distinctive feature of the reaction of DAST with the β-D -arabinoside 12 consists in the formation of a 3- or 5-benzylideneoxoniumyl-substituted intermediate on one of the consecutive transformations, which finally give rise to the inversion of the configuration at C(3) affording the xylosides 17 (18%) and 18 (55%); the lyxoside 14 was also isolated from the reaction mixture in a yield of 25% (Scheme 3). In the presence of the non-participating 5-O-trityl group, i.e., from the reaction products of 21 with DAST, the compounds 23 and 24 were isolated in 16 and 52% yield, respectively (Scheme 4). It may be thus reasonable to conclude that, in the case of the β-D -arabinosides 12 and 21 , the principal route of the reaction is the formation of the intermediate C(2)−O−SF₂NEt₂ derivative. Unlike 21 , the α-D -arabinoside 26 was converted to the lyxo-epoxide 25 (53%) and the lyxoside 27 (14%), which implies the intermediate formation of the C(3)−O−SF₂NEt₂ derivative (Scheme 5).     

Synthesis of Deoxy and Deoxyhalogeno Analogues of myo-Inositol

Abstract

A number of deoxy and deoxyhalogeno analogues of moyo-inositol of Interest 1n Investigating the biochemical processes of the phosphoinositide pathway were synthesized. Syntheses Include those deoxyinositols (cyclohexane pentols) which correspond to myo-inositol deoxygenated at positions 1, 4 and 5, as well as a set of 5-deoxyhalogeno (F, Cl, Br, I) myo- and epimeric neo-inositols. Configurational assignments are based primarily on ¹H NMR spectroscopy.     

Deoxy Derivatives of L-like 5'-Noraristeromycin

Several base variations of 2'- and 3'-deoxy derivatives of (+)-4'-deoxy-5'-noraristeromycin have been prepared from enantiomerically pure precursors following standard purine nucleoside construction. These carbocyclic nucleosides were evaluated against hepatitis B virus (HBV) and found to be inactive. No cytotoxicity to the cell line was observed.     

Reactions of Azides of Sugars with Derivatives of Tri-Valent Phosphorus Leading to N-Phosphorylated Sugars

Abstract

This communication deals with a simple method for preparation of X-phosphorylated sugars by the reaction of trivalent phosphorus derivatives with 1-α,β-azides of 2,3,4,5-tetraacetylated and 2,3,4,6-tetra(trimethyl)silylated glycose. It has been established that ohosphimine derivatives, obtained as a result of the Staudinger reaction, can be easily hydrolyzed to give derivatives of acetylated glucosaminphosphoric acids. It has been discovered that susceptibility to hydrolysis depends on the phosphorus suhstituents. When using esters of trivalent phosphorus the rate of hydrolysis for compounds with alkyl substituents decreases in order

C₃H₇ > C₂H⁵O >> CH₃O

This can probably be explained by the electronic and steric influence of the alkyl groups.     

1,5-Anhydro-D-Fructose: Stereoselective Conversions to 1,5-Anhydroalditols and Deoxy/Amino Substituted Analogues

ABSTRACT

1,5-Anhydro-D-fructose (1) has been converted into crystalline oximes. 1,5-Anhydroalditols and 2-amino-2-deoxy-1,5-anhydroalditols have been prepared by stereoselective reduction procedures from 1 and from the oximes, respectively.     

Synthesis of Sugars From D-Ribonolactone. II. An Alternative Synthesis of D-Erythrose

D-Erythrose was synthesized in four steps from D-ribono-1,4-lactone via the 3,5-O-benzylidene derivative of the latter compound. Reduction of the benzylidene D-ribonolactone, and periodate cleavage of the resulting 3,5-O-benzylidene-D- ribitol were performed in a one-flask reaction. The ensuing 2,4-O-benzylidene-D-erythrose was hydrolyzed with 10% acetic acid to obtain syrupy D-erythrose.     

A Convenient,Highly Efficient One-Pot Preparation of Peracetylated Glycals From Reducing Sugars

ABSTRACT

A convenient, highly efficient, one-pot, three-step procedure has been developed for the synthesis of peracetylated glycal derivatives from various reducing sugars including D-glucose, D-galactose, L-rhamnose, L-arabinose, D-maltose, D-lactose, and maltotriose. This procedure involves peracetylation of the reducing sugars with acetic anhydride and HBr/acetic acid followed by the transformation of the anomeric acetates to the corresponding bromides with additional HBr/acetic acid and finally reductive elimination of the 1-bromo and 2-acetoxy groups with Zn/CuSO₄·5H₂O in acetic acid/water containing sodium acetate. The overall yields of purified peracetylated glycals from the corresponding sugars range from 50 - 98%.

     

单糖化学催化制取运输燃料

农作物秸秆和林业废弃物是资源量大、可再生的非粮生物质。它们由半纤维素、纤维素和木质素组成,源于这些生物质的单糖不仅可以经过生物催化过程制备纤维乙醇,还是化学催化法制备传统烃类运输燃料的重要平台。本文首先介绍了木质生物质酶法和酸催化法水解制备单糖的工艺特点,然后详细介绍了近几年来开发的从单糖出发制取烃类生物燃料的各种新型催化方法,如单糖直接HZSM-5分子筛催化重整制备液体烃类,以及单糖经乙酰丙酸和酯化加氢工艺、经多元醇和水相脱水加氢（APD/H）工艺、经糠醛类化合物和羟醛缩合加氢工艺、经单官能团化合物和催化提质工艺。对这些催化方法的工艺条件、催化剂组成和化学反应进行了总结评述。考虑到由单糖制备C₆以上烃类可以直接或混配为传统的液体燃料,本文对这两条工艺路线进行了重点介绍,总结了过程所发生的反应和脱氧机理,并探讨了工业化过程中需要注意的科学难题。     

Reduction of 1-Deoxy -13–oxotaxanes

Numerous reports have described the semisynthesis of paclitaxel and its anologues from different taxoids 1. However, to the best of our knowledge almost all taxoids have a C-1-hydroxyl. Heretofore, the semisynthesis from taxinine, an abundant natural taxoid lacking of C-1-hydroxyl, has only reached the point of C-13 ketone intermediate 2. We have also encountered difficulties in reducing C-13 ketone to corresponding α- hydroxy group using the same conditions as in total synthesis of paclita…     

Oxazolidines From Sugars. III. A New Method for N-Alkyl and N,N-Dialkyl-D-Glucosamine Derivatives

Abstract

Title compounds can be synthesised by an easy two-step method from the readily available benzyl 2-acylamino-4,6-O-benzylidene-2-deoxy-D-glucopyranosides (1–5), by nucleophilic cleavage of the oxazolidine ring previously formed between the positions 2 and 3 of the aminosugars.     

A Practical Approach to the Synthesis of Dianhydro Sugars

Chiral tetrols derived from various carbohydrate precursors have been converted into the corresponding dianhydro sugar derivatives in a one pot procedure. The course of reaction very much depends upon the protecting groups used. In case of D-mannitol and sorbitol, it has been shown that when 3,4-hydroxy groups are protected as trans-acetonide group, the present methodology furnished exclusively 1,2: 5,6-dianhydro derivatives in excellent yield. However, if the 3,4-hydroxy groups are protected with benzyl group a mixture of products consisting of dianhydro sugar, a furan and a bicyclo[2.2.2]octane derivatives were obtained. This method has also been used to synthesize dianhydro sugars in which the two diol moieties are placed adjacent to each other or separated by one or more carbon atoms.     

An Improved Method to Resolve Plant Saponins and Sugars by TLC

Thin-layer chromatography (TLC) plays an important role in the initial selection of mutants having a unique seed saponin composition from the germplasm collections of the subgenus Soja. In the conventional TLC procedure, the dehydrated free sugars are retained just below the major saponins and interrupt the identification of some minor saponin constituents. To resolve this problem, we developed an efficient and reliable method to move sugars from the saponin area on TLC. A developing chamber was saturated with the lower phase of chloroform:methanol:water (65:35:10, v/v) for 2?h and the TLC plates were developed in it for 50?min. Plates were then dried at 100?°C for 10?min to evaporate the excess mobile phase and developed again with 10?% H₂SO₄ for 15?min. While sulfuric acid migrates over the surface of SiO₂, sugar molecules are dehydrated and hydrophilic interactions between free sugars and SiO₂ are strongly reduced. Thus, the positions of dehydrated sugars were shifted to above the saponin area on the TLC plate. This resulted in easy recognition of the saponin composition without any discrimination. This amended protocol would be applicable to all TLC analyses in which the target components should be separate from the interrupting sugar molecules.     

Characterization of Orange Peel Waste and Valorization to Obtain Reducing Sugars

Annually, millions of tons of foods are generated with the purpose to feed the growing world population. One particular eatable is orange, the production of which in 2018 was 75.54 Mt. One way to valorize the orange residue is to produce bioethanol by fermenting the reducing sugars generated from orange peel. Hence, the objective of the present work was to determine the experimental conditions to obtain the maximum yield of reducing sugars from orange peel using a diluted acid hydrolysis process. A proximate and chemical analysis of the orange peel were conducted. For the hydrolysis, two factorial designs were prepared to measure the glucose and fructose concentration with the 3,5-DNS acid method and UV-Visible spectroscopy. The factors were acid concentration, temperature and hydrolysis time. After the hydrolysis, the orange peel samples were subjected to an elemental SEM-EDS analysis. The results for the orange peel were 73.530% of moisture, 99.261% of volatiles, 0.052% of ash, 0.687% of fixed carbon, 19.801% of lignin, 69.096% of cellulose and 9.015% of hemicellulose. The highest concentration of glucose and fructose were 24.585 and 9.709 g/L, respectively. The results highlight that sugar production is increased by decreasing the acid concentration.     

An Improved Method to Resolve Plant Saponins and Sugars by TLC

Thin-layer chromatography (TLC) plays an important role in the initial selection of mutants having a unique seed saponin composition from the germplasm collections of the subgenus Soja. In the conventional TLC procedure, the dehydrated free sugars are retained just below the major saponins and interrupt the identification of some minor saponin constituents. To resolve this problem, we developed an efficient and reliable method to move sugars from the saponin area on TLC. A developing chamber was saturated with the lower phase of chloroform:methanol:water (65:35:10, v/v) for 2 h and the TLC plates were developed in it for 50 min. Plates were then dried at 100 °C for 10 min to evaporate the excess mobile phase and developed again with 10 % H₂SO₄ for 15 min. While sulfuric acid migrates over the surface of SiO₂, sugar molecules are dehydrated and hydrophilic interactions between free sugars and SiO₂ are strongly reduced. Thus, the positions of dehydrated sugars were shifted to above the saponin area on the TLC plate. This resulted in easy recognition of the saponin composition without any discrimination. This amended protocol would be applicable to all TLC analyses in which the target components should be separate from the interrupting sugar molecules.