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1.
The condensation of the acetoxyisoxazolidines with silylated uracil, thymine, cytosine, N-acetylcytosine, and guanine proceeded in good yields and with moderate to good stereoselectivity to give isoxazolidinyl β- and α-nucleosides. The stereoselectivity of the addition is dependent on the structure of the substituent at C-3 originating from the starting chiral nitrone. The Vorbrüggen nucleosidation of isoxazolidine 8 at 70 °C afforded β-anomers as the exclusive nucleosides together with the isoxazoline 11. It was found that the nucleosidation proceeded also in methylene chloride at room temperature. 相似文献
2.
Enantiospecific enzymatic hydrolysis of rac-5-arylhydantoins is described. Immobilized d-hydantoinase from Vigna angularis was used to produce with 100% conversion and over 98% enantiomeric excess N-carbamoyl-d-p-fluorophenylglycine and N-carbamoyl-d-p-trifluoromethylphenylglycine. 相似文献
3.
Luigi A. Agrofoglio Franck Amblard Steve Charamon Thomas A. Zevaco 《Tetrahedron》2004,60(38):8397-8404
The enantiomeric synthesis of l-cyclopentenyl nucleosides is described. The key intermediate (+)-cyclopentenyl alcohol (8) was prepared from methyl-α-d-galactopyranoside 1 using a ring closing metathesis reaction. Transformation of the allylic alcohol 8 into the allylic acetate (9) or carbonate (10), allows their coupling with purine and pyrimidine bases under Pd(0)-catalyzed Tsuji-Trost allylic alkylation's to yield 12a-c. The Pd catalyzed reaction was found to require the use of AlEt3. 相似文献
4.
B.Gopal ReddyYashwant D Vankar 《Tetrahedron letters》2003,44(25):4765-4767
Methyl N-acetyl-α-d-lividosaminide has been synthesised starting from 4,6-di-O-benzyl-d-glucal via a new nitro glucal derivative in six steps. 相似文献
5.
R. Fernando Martínez Martín Ávalos Pedro Cintas Mark E. Light Esther M.S. Pérez 《Tetrahedron》2008,64(27):6377-6386
A one-pot procedure for preparing chiral 1,3-oxazolidines derived from N-methyl-d-glucamine and aryl aldehydes is described. It has been carried out by using readily available reagents and operationally simple conditions allowing the preparation of the acyclic C-nucleoside analogs in high yields. The structure of these derivatives has been fully characterized by NMR correlations and single-crystal X-ray diffraction. Some reactions also provide access to the corresponding tetrahydro-1,3-oxazines by an alternative ring closure. Mechanistic considerations account for the observed steric course. 相似文献
6.
Céline Falentin 《Tetrahedron letters》2009,50(38):5364-1987
d-Ribono-1,4-lactone was treated with ethylamine in DMF to afford N-ethyl-d-ribonamide 9a in quantitative yield. Bromination of amide 9a by the system SOBr2 in DMF or PPh3/CBr4 in pyridine led, after acetylation, to epoxide 7. However, treatment of amide 9a with acetyl bromide in dioxane followed by acetylation gave 2,3,4-tri-O-acetyl-5-bromo-5-deoxyl-N-ethyl-d-ribonamide 10a. Methanolysis of 10a, with sodium methoxide, afforded the N-ethyl-d-ribonolactam 11a in 51% overall yields. Using this method, N-butyl, N-hexyl, N-dodecyl, and N-benzyl-d-ribonolactams 11b-e were obtained in good yields (48-53%). 相似文献
7.
A key intermediate corresponding to a rare sugar framework has been synthesized, starting from d-xylose, an inexpensive carbohydrate. This approach gave access to new elaborated sugar moieties for structure–activity relationships in the KRN research. 相似文献
8.
Lacosamide is an important anti-epilepsy drug and O-methyl-d-serine is a relevant intermediate in the synthesis of lacosamide. Optically active O-methyl-d-serine was prepared by using a chemoenzymatic method from inexpensive acrylamide. Our method is a four-step reaction sequence: bromination of acrylamide; etherification of dibromopropionamide; ammonolysis of α-bromo-β-methoxy-propionamide; enzymatic racemization and selective hydrolysis. The double-enzyme catalyst system, which consists of α-amino-ε-caprolactam racemase (Locus, E01594) and d-stereospecific amino-acid amidase (Locus, AB026907), was successfully applied to produce enantiopure O-methyl-d-serine (ee >99.8%) in high yield (>98.5%). Optically active O-methyl-d-serine was obtained with a total yield of 81.3%. 相似文献
9.
Stephen G. Davies Ai M. FletcherEmma M. Foster James A. LeePaul M. Roberts James E. ThomsonMichael A. Waul 《Tetrahedron》2014
A range of the methyl glycosides of 2-deoxy-2-aminohexoses, comprising d-allosamine, d-mannosamine, d-idosamine and d-talosamine, were prepared from the corresponding d-aldopentoses via a seven step synthetic sequence. The doubly diastereoselective conjugate addition of the requisite antipode of lithium N-benzyl-N-(α-methylbenzyl)amide and in situ enolate oxidation with the requisite antipode of camphorsulfonyloxaziridine (CSO) was used as the key, stereodefining step. Sequential reduction of the resultant α-hydroxy-β-amino esters and oxidative cleavage of the C(1)–C(2) diol unit furnished the corresponding α-amino aldehydes. Subsequent N- and O-deprotection gave the target compounds (as mixtures of anomers) in good yield and high diastereoisomeric purity. 相似文献
10.
Michaël Bosco Sophie Le Gall Christophe Rihouey Muriel Bardor Xavier Pannecoucke 《Tetrahedron letters》2008,49(14):2294-2297
A new strategy to tag glycoproteins carrying terminal GlcNAc was developed using commercially available bovine β-1,4-galactosyltransferase (GalT) and UDP-6-azidogalactose. The azide function was then allowed to react via a biotinylated Staudinger-Bertozzi probe demonstrating the usefulness of such a procedure to tag any glycoprotein possessing a N-acetylglucosamine terminal residue from any type of cell lysate. 相似文献
11.
Omar Hassan OmarFrancesco Babudri Gianluca M. Farinola Francesco NasoAlessandra Operamolla Adriana Pedone 《Tetrahedron》2011,67(2):486-494
Phenylene-thiophene oligomers bearing peracetylated β-d-glucose or N-BOC-l-phenylalanine as chiral substituents were synthesized in good yields by a versatile protocol based on the Suzuki-Miyaura cross-coupling reaction. Aryl iodides bearing the chiral biomolecules as substituents efficiently reacted with pinacol boronates of bi- or terthiophenes leading to the bio-functionalized oligomers in good yields. 相似文献
12.
Cristina Chamorro 《Tetrahedron》2004,60(49):11145-11157
Screening of a combinatorial CTV-based artificial, synthetic receptor library 1 {1-13, 1-13, 1-13} for binding of a variety d-Ala-d-Ala and d-Ala-d-Lac containing ligands (6-11) was carried out in phosphate buffer (0.1 N, pH=7.0). After screening and Edman sequencing, synthetic receptors were found containing amino acid sequences, which are either characteristic for binding dye labeled d-Ala-d-Ala or d-Ala-d-Lac containing ligands. For example, receptors capable of binding d-Ala-d-Ala containing ligands 6, 7, 9 and 11 contained—almost in all cases—at least one basic amino acid residue—predominantly Lys—in their arms. This was really a striking difference with the arms of the receptors capable of binding d-Ala-d-Lac containing ligands 8 and 10, which usually contained a significant number of polar amino acids (Gln and Ser), especially in ligand 8, but hardly any basic amino acids. Use of different (fluorescent) dye labels showed that the label has a profound, albeit not decisive, influence on the binding by the receptor. A hit from the screening of the CTV-library with FITC-peptidoglycan (6) was selected for resynthesis and validation. 相似文献
13.
A stereoselective and scalable route to 1,5-anhydrohexitol nucleoside analogues belonging to l-series as building blocks for l-HNA oligonucleotide synthesis has been efficiently tuned. Key to the successful outcome of our approach is the development of a DDQ-mediated domino reaction, which leads to the formation of an unsaturated 1,6-anhydrosugar derivative. Sugar elaborations and base insertion then enable to synthesize six-membered nucleosides. 相似文献
14.
The Baylis-Hillman reaction of 3-O-benzyl-α-d-xylo-pentodialdo-1,4-furanose 2 afforded a diastereomeric mixture of l-ido- and d-gluco-configurated α-methylene-β-hydroxy esters 3a and 3b, respectively, in 1:1 ratio. Conjugate addition of benzyl amine on 3a gave adduct 4a as a major product while, addition of benzyl amine to 3b gave only one diastereomer 4b. Reduction of ester functionality in 4a/4b, opening of 1,2-acetonide functionality followed by reductive amino-cyclization under hydrogenation condition afforded azocanes 1c/1d in good yield. 相似文献
15.
Amit Kumar 《Tetrahedron》2008,64(10):2379-2390
Four hybrids of azasugars with d-glucose and d-galactose have been synthesized from 3-nitro-2,3-unsaturated-O-glycosides. All the hybrid molecules showed moderate activity against β-galactosidase, the one derived from d-glucose and 1,4-dideoxygulonojirimycin 18, and 26, which is a hybrid of d-glucose and 1,4-dideoxymannohomonojrimycin, showed selectivity toward α-glucosidase and β-galactosidase, respectively. 相似文献
16.
Uwe EilitzChristoph Böttcher Lothar HennigAlois Haas Cecile BoyerKlaus Burger 《Journal of fluorine chemistry》2002,115(2):149-154
Homochiral 2-C-perfluoroalkyl substituted d- and l-riboses were synthesized via Barbier, Grignard and Ruppert type reactions. The influence of the size of the perfluoroalkyl groups, attached to C-2, on the furanose/pyranose as well as on the α-furanose/β-furanose and α-pyranose/β-pyranose ratio in solution was studied. 相似文献
17.
Xuequan Lu 《Tetrahedron letters》2005,46(18):3165-3168
The preparations of d-ribo- and l-lyxo-phytosphingosines (1, 2) are described. Chelation-controlled addition of tetradecylmagnesium bromide to pentylidene-protected d-threitol aldehyde 6 afforded the key intermediate tetrol 7, providing the desired l-lyxo stereochemistry of phytosphingosine. Inversion at C4 of intermediate 7 provided the d-ribo stereochemistry. 相似文献
18.
Fluoroolefin peptidomimetics of the dipeptide N-acetyl-Glu-Ala were synthesized via an Evans asymmetric aldol reaction and an Overman rearrangement. This dipeptide is the N-terminal of an octapeptide implicated in the signal transduction via PKCε. 相似文献
19.
Starting from a single suitable functionalised epoxide, a highly efficient stereoselective synthesis of d-erythro-sphingosine and d-lyxo-phytosphingosine is described. The approach allows the formal preparation of all stereoisomers of these sphingoid structures. 相似文献
20.
Jagadish Pabba 《Tetrahedron letters》2005,46(21):3619-3622
The d-gluco-, l-ido-, d-galacto-, and l-altro-configured glycaro-1,5-lactams 1-4 were prepared from the known tartaric anhydride 5 via the aldehyde 6. These lactams are known (1) or potential (2-4) inhibitors of β-d-glucuronidases and α-l-iduronidases. Olefination of 6 to the (E)- and (Z)-alkenes 7 or 8, followed by reagent or substrate controlled dihydroxylation, lactonization, azidation, reduction, and deprotection led in 10 steps and in overall yields of 11-20% to the title lactams. 相似文献