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1.
《Tetrahedron: Asymmetry》1998,9(13):2245-2251
Lithiated oxazolo[3,4-a]benzimidazole 4 reacted with various alkyl halides to give oxazolo[3,4-a]benzimidazoles 5a–d in good yields as single diastereoisomers. (R)-Benzimidazol-2-yl carbinols 6a–d were obtained upon hydrolysis under acidic conditions of 1H,3H-oxazolo[3,4-a]benzimidazole derivatives. 相似文献
2.
Photooxygenations of 2-(γ,ε-dihydroxyalkyl) furans in H(2)O followed by in situ reduction and ketalization affords, in one synthetic operation, DE-bicyclic ketals of the pectenotoxins. 相似文献
3.
《Tetrahedron: Asymmetry》1999,10(17):3381-3389
Enantiopure 3-(ω-hydroxyalkyl)-2-pyrrolidinones 7 and 9 were synthesised by Michael-addition of nitromethane to chiral α-alkylidenelactones 1 followed by reduction of the resulting 3-(β-nitroalkyl)-lactones and ring transformation of the intermediate 3-(β-aminoalkyl)-lactones. In an analogous manner the naturally occurring costuslactone 10 was transformed into the butyrolactam 12. 相似文献
4.
《Tetrahedron: Asymmetry》2001,12(6):949-957
This report describes the synthesis of enantiomerically pure (S)- and (R)-α-methylserines on a multigram scale, starting from the Weinreb amide of 2-methyl-2-propenoic acid and using a stereodivergent synthetic route that involves a Sharpless asymmetric dihydroxylation reaction. As a synthetic application of these quaternary α-amino acids, they were used as starting materials in the synthesis of the well-known valuable homochiral (S)- and (R)-N-Boc-N,O-isopropylidene-α-methylserinal building blocks. 相似文献
5.
A. N. Blinnikov S. Kulikov N. N. Makhova L. I. Khmel'nitskii 《Russian Chemical Bulletin》1996,45(7):1692-1698
A general and simple preparative method for the synthesis of -hydroxyalky(benzyl)furazan and -furoxan derivatives is proposed, The method involves reduction of acyl or ethoxycarbonyl substituents in these heterocyclic compounds with NaBH4 in ethanol. Based on the alcohols thus prepared, a number of previously unknown functional derivatives (-nitroxyalkyl--haloalkyl-, and -azidoalkylfurazans and -furoxans) have been synthesized.Translated fromInvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7. pp, 1782–1788, July, 1996. 相似文献
6.
Gryparis C Lykakis IN Efe C Zaravinos IP Vidali T Kladou E Stratakis M 《Organic & biomolecular chemistry》2011,9(16):5655-5658
Photooxygenation of (β-keto)-2-substituted furans leads, in a one pot operation, to functionalized 3(2H)-furanones with good to excellent yields. This methodology was applied as a key-step to the concise and biomimetic synthesis of the sesquiterpene merrekentrone C. The precursor to merrekentrone C, keto difuran, was synthesized using a cross coupling of α-iodo-3-acetylfuran with an alkenyl furan under Fenton-type conditions. 相似文献
7.
Paulo A. Machicao Scott R. Burt Ryan K. Christensen Nathan B. Lohner J.D. Singleton Matt A. Peterson 《Tetrahedron letters》2017,58(24):2318-2321
Treatment of N-[(4-hydroxy-6-phenyl)pyrimidin-2-yl]cyanamide with 1° alkyl or arylamines in isopropyl alcohol for only 10 min at 110–120 °C under microwave conditions gave the corresponding N′-alkyl(aryl)guanidine derivatives in excellent yields (65–84%). Isolated yields were greatest when >1.0 equiv. of amines were employed, but excellent results were also obtained when aryl and alkylamines were reacted with a more atom-economical loading (1.0 equiv.; 70% and 72% ave. yields, respectively). Arylamines with either highly electron withdrawing substituents (e.g. CO2H) or pi-deficient heterocycles (e.g. variously substituted aminopyridines) did not work well under these conditions, and reaction with ureas and/or amino acids did not give detectable products. Work-up was exceedingly simple, and involved simple collection and washing of product on a sintered glass funnel. Products were obtained in analytically pure form and required approximately 1 h to prepare, start to finish. 相似文献
8.
Guillaume Poisson Florence Dumarçay-Charbonnier Alain Marsura 《Tetrahedron letters》2012,53(16):2082-2087
This Letter describes the synthesis of a C3-symmetrical tris-ACE-(6,6′-bipyridyl)-α-CyD via ‘one-pot’ Staudinger-Aza-Wittig reaction (SAW). Metal complexation behavior was investigated by UV–vis and Circular Dichroism. Coordination of 6,6′-bipyridyl units with CuII and NiII cations, spontaneously generates a strong exciton coupling-type positive Cotton effect proving the formation of a Λ-helix with a left-handed screw propeller (M). 相似文献
9.
The asymmetric synthesis of 16,17,20-epi-deserpidine and a derivative of(-)-deserpidine has been achieved.Key feature s in the assembly of the pentacyclic framework include a visible-light photocatalytic intra-/inter-/intramolecular radical cascade reaction to construct the tetracyclic ABCD ring system in one-pot and an intramolecularaldol reaction to forge the cyclohexane E ring. 相似文献
10.
Mark York 《Tetrahedron letters》2011,52(47):6267-6270
A synthesis of di-, tri- and tetra-substituted furans from reaction of the corresponding ketones and α-haloketones with LiHMDS is reported. Reaction under continuous-flow conditions gave increased yields and removed the need for external cooling when compared to the unoptimised batch conditions. 相似文献
11.
A simple two-step method for the selective preparation of anomerically pure 1α- and 1β-(indol-2-yl)deoxyribose derivatives was developed. The synthesis was based on the Sonogashira reaction of 1α- and 1β-ethynyldeoxyribose and 2-haloanilines followed by a Pd-complex catalyzed cyclization to the corresponding indolyldeoxyribosides. 相似文献
12.
Palakodety Radha Krishna Bonepally Karunakar Reddy Palabindela Srinivas 《Tetrahedron》2012,68(3):841-845
Total synthesis of 2-(2-hydroxyalkyl)-piperidine alkaloids, (?)-halosaline and (?)-8-epi-halosaline is reported from n-butyraldehyde using iterative asymmetric allylation, nucleophilic substitution with an azide and ring-closing metathesis as the key reactions. 相似文献
13.
《Tetrahedron letters》1986,27(15):1723-1726
α-Metallo benzylselenides and α-metallo selenoacetals derived from aromatic aldehydes have been conveniently prepared by metallation of the corresponding carbon acids. KDA in THF proved among the various basic systems tested, the most efficient.α-Metallo benzylselenides and α-metallo selenoacetals derived from aromatic aldehydes have been conveniently prepared by metallation with KDA of the corresponding carbon acids. These reactions have been used for the synthesis of arylalkanes, including those bearing a trialkylated benzylic carbon, from aromatic aldehydes. 相似文献
14.
The conjugate addition of lithium (R)-N-phenyl-N-(α-methylbenzyl)amide to a range of α,β-unsaturated 4-methoxyphenyl esters proceeds with excellent levels of diastereoselectivity to give the corresponding β-amino esters in good yield and as single diastereoisomers (>99:1 dr). The synthetic utility of this methodology has been demonstrated via the short and concise asymmetric synthesis of the tetrahydroquinoline alkaloid (R)-(-)-angustureine in six steps and 32% overall yield from commercially available oct-2-enoic acid. 相似文献
15.
《Tetrahedron: Asymmetry》1999,10(4):679-687
Kinetic resolution of 1,1,1-trifluoro-2-alkanone cyanohydrin acyl derivatives with Candida rugosa lipase afforded the remaining (R)-enantiomer in high selectivity (E from 30 to >200). Candida rugosa lipases from several suppliers were compared and found to differ remarkably in their selectivity. The (R)-enantiomer was hydrolyzed in one step to yield optically pure (R)-α-trifluoromethyl-α-hydroxycarboxylic acids in excellent yield. The (S)-acids were obtained in good e.e. by subtilisin-catalyzed resolution of the corresponding racemic esters followed by chemical hydrolysis of the remaining (S)-esters. 相似文献
16.
Belokon" Yu. N. Maleev V. I. Savel"eva T. F. Ikonnikov N. S. 《Russian Chemical Bulletin》2001,50(6):1037-1040
Both enantiomers of -methylserine were synthesized with the use of NiII complexes based on the chiral recyclable reagent (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide. Intermediate diastereomeric complexes were separated by crystallization of their O-acetyl derivatives. 相似文献
17.
Sajal Kumar Das 《Tetrahedron》2008,64(19):4162-4173
The enantioselective synthesis of benzo-annulated oxa-heterocycles 2,3-dihydrobenzofuran and 1-benzopyran derivatives is described using β-hydroxy-α-tosyloxy esters as chiral building blocks, which are easily accessible through the regioselective α-tosylation of Sharpless asymmetric dihydroxylation-derived syn-2,3-dihydroxy esters. 相似文献
18.
《Tetrahedron: Asymmetry》2000,11(4):879-887
A short and efficient enantioselective synthesis of (S)- and (R)-configured 6-hydroxy-8-nonene-carboxylates — precursors to (R)-α-lipoic acid and its (S)-enantiomer — by allylation of alkoxycarbonyl substituted aldehydes with allyltrimethylstannane and BINOL/Ti(OiPr)4 catalyst is described. The best results in terms of enantiomeric purity and yield are obtained employing 10 mol% of the titanium-species without molecular sieves. 相似文献
19.
20.
Maura Marinozzi 《Tetrahedron》2009,65(34):7092-1387
The metal-catalyzed reactions of neopentyl α-diazomethanesulfonate (DAMS) and diisopropyl α-diazomethanephosphonate (DIDAMP) with furan, 2-methylfuran and 2-methoxyfuran are reported. The products consist mostly of ω-acyl-substituted sulfono- or phosphonobutadienes and exo-cyclopropane derivatives. Treatment of the multicomponent reaction mixtures with iodine afforded exclusively the corresponding (E,E)-sulfono- and phosphono-ω-acylfunctionalized dienes, thus providing a short and efficient synthetic route to these hitherto unreported classes of compounds. 相似文献