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1.
Ana Calvo-mateo María-José Camarasa Angel Díaz-Ortíz Federico G. De las Heras Antonio Alemany 《Journal of carbohydrate chemistry》2013,32(3):395-404
Abstract Aldol reaction of 1,2-O-isopropylidene-5-O-tertbutyl-dimethylsilyl-α-D-erythro-pentofuranos-3-ulose (1) with acetone in the presence of aqueous K2CO3 afforded 3-C-acetonyl-1,2-O-isopropylidene-5-O-tertbutyl-dimethylsilyl-α-D-ribofuranose(2). Similar reaction of 1,2:5, 6-di-o-isopropylidene- α-D-ribo-hexofuranos-3-ulose (3) afforded 3-C-acetonyl-1,2:5, 6-di-o-isopropylidene- α-D-allofuranose (4) and (1R, 3R, 7R, 8S, 10R)-perhydro-8-hydroxy-5,5,10-trimethyl-2,4,6,11,14-pentaoxatetracyclo[8,3,1,01,8,03,7] tetradecane. The stereochemistry of the new chiral centers were determined by 1H NOE experiments. 相似文献
2.
Abstract Regioselective cleavage of 1,6-anhydro-maltose (1) with periodate and the subsequent recyclization with nitromethane gave 1,6-anhydro-3′-deoxy-3′-nitro-disaccharides (3). Three diastereomers, prepared by benzylidenation of 3, were separated by column chromatography. Each of 4′,6′-O-benzylidene derivatives successively underwent debenzylidenation, reduction of the nitro group, and peracetylation to give 3′-acetamido-3′-deoxy-disaccharide derivatives (7, 8, and 9). The configurations of the 3-amino sugar moietres in 7 (D-gluco), 8 (D-manno) and 9 (D-galacto) were determined on the basis of the 1H NMR data. The main product (7) was further modified to the 6-deoxy-6-nitro derivative. 相似文献
3.
During the investigation into methods of converting loganin (1) into secologanin (2, R=β-D-glucose), the lead tetraacetate fragmentation reaction1 of the four diastereomeric loganin aglucone O-methyl ethers 4, 6, 9, and 11, was studied. 相似文献
4.
α-Dithiophosphates of peracetylated 2-deoxyhexc-pyranoses, 1a, 1b and 2, uhich are easily prepared by addition of organic phosphorodithioic acids to glycais react smoothly with resin-bound 2- and 4-nitrophenoxides to give stereoselectively the respective nitrophenyl 2-deoxy-β-D-hexopyranosides (3, 4, 5 and 6) in high yields. Glycosylation of the 2, 4-dinitro'phenoxide, however, leads with comparable stereoselectivity to 2,4-dinitrophenyl 2-deoxy- α-D-hexopyranosides (7 and 8). Glycosides 3 - 6 are quantitatively deacetylatec by Amberlyst A-26 (OH-), whereas glycosides 7 and 8, under the same reaction conditions undergo splitting of the O-glycosidic bond. 相似文献
5.
Manfred Regitz Wolfgang Rösch Thomas Allspach Ulrich Annen Karsten Blatter Jürgen Fink 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):479-482
Abstract The syntheses of phospholes (7, [3+2]-cycloaddition), bicyclophosphaalkenes (17, [4+2]-cycloaddition), and phosphabenzenes (15, [4+2]-cycloaddition followed by an extrusion process) starting from the phosphaalkynes (4) are described. The 2–Dewar phosphabenzene 18, obtained from the cyclobutadiene 21 and 4 (R =tBu), is the starting material for the synthesis of the valency isomers 19, 20, 22, and 23. 相似文献
6.
Burdica Ljevaković Jaroslav Horvat Branimir Klaić Srdanka Tomić 《Journal of carbohydrate chemistry》2013,32(3):263-278
Abstract Fully protected 1-thioglycopyranosyl esters of N-acylamino acids (5, 6, and 7) were prepared by condensation of methyl 2, 3, 4-tri-O-acetyl-1-thio-β-d–glucopyranuronate (1), 2, 3, 4-tri-O-acetyl-1-thio-l–arabinopyranose (2), and 2, 3, 4-tri-O-acetyl-1-thio-D-arabinopyranose (3) with pentachlorophenyl esters of N-acylamino acids in the presence of imidazole. The 13C NMR chemical shifts of the starting 1-thio sugars and the 1-thiol ester products are reported. 相似文献
7.
Abstract The reaction of N-phenyliminoketenylidenetriphenylphosphorane [a] (1), with 2-benzylidene-1, 3-indandione (2), 1,2-diphenyl-3,4-pyrazolidenedione (3)and/or 5-benzylidene barbituric acid (4) has been investigated. When ylide 1 was allowed to react with compounds 2, 3 or 4 in THF at ambient temp. the corresponding new pyrano-phosphoranylidenes 5, 6 or 7 were obtained. The elemental microanalyses, IR, 1H NMR, 31P NMR and MS data agree with the structure of the cyclic iminophosphoranes by [4+2]-cycloaddition and exclude 4-membered ring structure by [2+2]-cycloaddition. When the Wittig reaction was carried on the pyrano-phosphoranes 5, 6 or 7 using p-nitrobenzaldehyde, the exocyclic olefins together with triphenylphosphine oxide were isolated. 相似文献
8.
In the course of a study on the photochemical and thermal behaviour of β,γ-δ,ε-dienones1-4, (E)-retro-α-ionone (2a) and a series of methylated (3, 4) and desmethyl analogues (2b-2e) have been synthesized by a simple deconjugative isomerization of the corresponding conjugated dienones in strong alkaline solution. 3-Methyl- (3) and 3,3-dimethyl-retro-α-ionone (4) have been prepared by addition of methyl chloride to a strongly alkaline solution of β-ionone (1a).5 相似文献
9.
A useful synthesis of 3-hydroxy-4-chromanone (6) is not currently available. Lead tetraacetate oxidation of 4-chromanone (4) yields the C(3) acetoxy derivative but this compound could not be deacetylated to 6.1 Recently Donnelly and Maloney reported2 that the Algar-Flynn-Oyamada reaction (H2O2/CH3OH/NaOH), which is commonly used for the conversion of o-hydroxychalcones (1) into 3-hydroxyflavanone (2) and 3-hydroxyflavones (3), does not yield 6 when applied to o-hydroxya-crylophenone 1 (R = H). The authors found that under less basic conditions using K2CO3 some 6 is formed but the major product is catechol. These observations clearly indicate the necessity of developing a method for making 6. The present note describes a staightforward way of preparing 3-hydroxy-4-chromanone (6) in good yield. 相似文献
10.
Recently some furanonaphthoquinones were isolated from Tabebuia species2,3,4. The structures la, lb2, and li4 were assigned to three of these compounds (those of la and lb being later confirmed by synthesis3,5,6). However, for the three other isolated compounds the spectroscopic data did not permit a decision to be made between the 2,3,4 - - - 4 isomeric pairs of structure lc and Id, le and lf 3, and lg and lh 4. Compounds la, lb, and le (or If), were tested in the KB cell culture assay and shown to be more active cytotoxic agents than lapachol2,3, the probable biogenetic precursor of all of them. 相似文献
11.
Several years ago a number of antihypertensive N-alkyl-N′-cyano-N″-pyridylguanidines was prepared by addition of cyanamide to N-alkyl-N′-pyridylcarbodiimides which were obtained from the respective thioureas and phosgene or triphenylphosphine/carbon tetrachloride1. Recently we have described some attractive synthetic methods for N-alkyl-N′-4-pyridylthioureas2, based on 4-pyridyldithiocarbamic acid (1) (Scheme 1). We now report on the synthesis of N-alkyl-N′-cyano-N″-4-pyridylguanidines (4) from (1) by two different routes which ultimately may pass through a common intermediate (3) (Scheme 1). 相似文献
12.
Abstract Glycosylation of methyl 3-O-(2-acetamido-3, 6-di-O-benzyl-2-deoxy-β-D-glucopyranosyl)-2,4,6-tri-O-benzyl-β-D-galactopyranoside (2) with 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide (1), catalyzed by mercuric cyanide, afforded a trisaccharide derivative, which was not separated, but directly O-deacetylated to give methyl 3-O-(2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-β-D-galactopyranosyl-β-D-giucopyranosyl)-2,4,6-tri-O-benzyl-β-D-galactopyranoside (8). Hydrogenolysls of the benzyl groups of 8 then furnished the title trisaccharide (9). A similar pflyccsylation of methyl 3-O-(2-acetamido-3-O-acetyl-2-deoxy-β-D-glucopyranosyl)-2,4,6-tri-O-benzyl- β-D-galactopyranoside (obtained by acetylation of 4, followed by hydrolysis of the benzylidene acetal group) with bromide 1 gave a tribenzyl trisaccharide, which, on catalytic hydrogenolysls, furnished the isomeric trisaccharide (12). Methylation of 4 and 2 with methyl iodide-silver oxide in 1:1 dichloro-methane-N, N-dimethylformamide gave the 3-O- and 4-O-monomethyl ethers (13) and (15), respectively. Hydrogenolysis of the benzyl groups of 13 and 15 then provided the title monomethylated disaechartdes (15) and (16), respectively. The structures of trisacchacides 9 and 12, and disaccharides 14 and 16 were all established by 13C MMR spectroscopy. 相似文献
13.
Michael D. Threadgill 《合成通讯》2013,43(12):1101-1105
In a report on the reaction of 2-chloronitrobenzene (1) with diethanolamine (2), Meltsner et al 1 claim that the expected SNAr product, N-(2-nitrophenyl)diethanolamine (3), is not formed; rather that the products are 2,2′-dichloroazobenzene (4), 2-nitrophenol (5), 2-chloroaniline (6) and 4-(2-aminophenyl)morpholine (7). Similar products in which the nitro function is reduced are also reported2 for the corresponding reaction with ethanolamine. In this laboratory, in an attempted preparation of 2,2′-dichloroazobenzene (4) for reference purposes in photochemical studies on the antineoplastic agent 5-(3-azido-4-chlorophenyl)-6-ethyl-pyrimidin-2,4-diamine3, the expected SNAr product (3) was obtained along with other products. 相似文献
14.
Tsutomu Tsuchiya Yoshiaki Takahashi Makoto Endo Sumio Umezawa Hamao Umezawa 《Journal of carbohydrate chemistry》2013,32(4):587-611
2′,3′-Dideoxy-2′-fluorokanamycin A (23) was prepared by condensation of 6-azido-4-0-benzoyl-2,3,6-trideoxy-2-fluoro-α-D-ribo-hexopyranosyl bromide (13) and a protected disaccharide (19). Methyl 4,6-0-benzylidene-3-deoxy-β-D-arabino-hexopyranoside (5) prepared from methyl 4,6-0-benzylidene-3-chloro-3-deoxy-β-D-allo-hexopyranoside (1) by oxidation with pyridinium chlorochromate followed by reduction with Na2 S2O4 was fluorinated with the DAST reagent to give methyl 4,6-O-benzylidene-2,3-dideoxy-2-fluoro-β-D-ribo-hexopyranoside (7). Successive treatment of 7 with NBS, NaN3 and SOBr2 gave 13. The structure of the final product (23) was determined by the 1H and 19F and shift-correlated 2D NMR spectra. 相似文献
15.
René Csuk Alois Fürstner Hermann Kalchhauser Christoph Kratky Ulrike Wagner Hans Weidmann 《Journal of carbohydrate chemistry》2013,32(3):401-409
The stereochemistry of the branched C-ethoxycarbonyl-methy.lene derivatives 1a, 1b, 2a, and 2b was evaluated by analysis of their 1H- and 13C-NMR shift data, unequivocally supported by NOE-effects clearly discriminating diastereomers. The X-ray-analysis of isomer 2a confirmed the NMR-data and provided the picture of its detailed structure. 相似文献
16.
Abstract Recently we have reported that the reaction of sodium methoxide with ate-complexes (1) readily prepared from trimethyl-silylpropargyl phenyl ether and organoboranes gives trimethyl-silylallenes (2) selectively (eq. 1).1 In an attempt to find a new synthetic application of such silylallenes (2), the oxidation of 2 was examined. Although the usual oxidants such as m-chloro-perbenzoic acid were found to be unsuitable for the oxidation of the silylallenes, it was discovered that 2 was autoxidized at room temperature to propargylic hydroperoxide (3) (eq. 2). For example, the acidified starch-iodine test2 strongly suggested the presence of the organic hydroperoxide in the reaction mixture obtained from 1,2-heptadienyltrimethylsilane (2, R=Bu) and oxygen. The hydroperoxide (3, R=Bu) was isolated in a 40% yield by distillation, 45–48 [ddot]C/0.1 mmHg. In the infrared spectrum, the OH stretching frequency appears at 3430 cm?1 and the C°C at 2180 cm,?1 相似文献
17.
Ronan Van Rijsbergen Marc Anteunis André De Bruyn 《Journal of carbohydrate chemistry》2013,32(2):329-333
When 1,6-anhydro-2-azido-4-O-benzoyl-2-deoxy-β-D-glucopyranose (1 (l) was treated with allyl bromide in benzene-tetrahydrofuran solution in the presence of sodium hydride, we obtained the expected reaction product, 3-O-allyl-1,6-anhydro-2-azido-4-O-benzoyl-2-deoxy-β-D-glucopyranose (2), and the rearranged compounds 1,6-anhydro-2-azido-3-O-benzoyl-2-deoxy-β-D-glucopyranose (3) and 4-O-allyl-1,6-anhydro-2-azido-3-O-benzoyl-2-deoxy-β-D-glucopyranose (4). 相似文献
18.
Heterobicycles of δ-lactam fused with imidazolidine (4, 7), hexahydropyrimidine (5, 8), or hexahydro-1, 3-diazepine (6, 9) were synthesized by the reaction of heterocyclic ketene aminals 1, 2 or 3 with ester of α,β-unsaturated carboxylic acids. 相似文献
19.
Recently, we required a convenient method for preparing the 3-formyl-cyclohexenone, 1, starting from dihydroresorcinol. The conversion of dihydroresorcinol into the cyclohexenone derivative 2, could be readily accomplished using the elegant method of Stork and Danheiser,1 however, existing methods for the transformation of the ketone group of 2 into the formyl group of 1 did not prove satisfactory.2 We describe here, a simple and general method for the transformation of 2 into 1 (Scheme I). 相似文献
20.
In recent syntheses of eburnamonine,1 aspidospermidine2 and quebrachamine2 the copper-catalyzed, diazoacetic ester-induced conversion of tetrahydropyridine 1 into the cyclopropanopiperidine 2 was a crucial, early reaction step. It became of interest to apply this reaction to dihydropyridine equivalents of 1, i.e. 3 and 4, in connection with the development of routes of synthesis directed towards alkaloids of the pandoline or velbenamine types. This Communication illustrates the preparation and cyclopropanation of dihydropyridines 3 and 4. 相似文献