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1.
The preparation of optically pure Nα-Me, Nβ-Boc-protected α-hydrazinoacids in large scale is described via a SN2 protocol. These compounds were used as starting materials for the synthesis of 1:1:1 [Nα-Me α-hydrazino/α/Nα-Me α-hydrazino]trimers.  相似文献   

2.
The sulfenylation of ketones having α-hydrogens has been achieved using N-chlorosuccinimide (NCS) under mild reaction conditions to produce α-ketothioethers in excellent yields with high selectivity. The use of NCS makes this method quite simple, convenient and practical.  相似文献   

3.
A large number of N-aminodipeptides compounds have been obtained via a Mitsunobu protocol performed in solution or by solid-phase synthesis. The oligomerization of some of them has been studied in solution or on solid support leading to the formation of 1:1[α:α-N-amino]mers.  相似文献   

4.
Santosh T. Kadam 《Tetrahedron》2010,66(9):1684-3742
In the presence of catalytic amount of bismuth bromide (5 mol %) the α-amido p-tolylsulfones are converted into N-acyliminium ions, which undergo the nucleophilic addition of trimethylsilyl cyanide (TMSCN) to provide the N-protected α-amino nitriles in very good yield. A variety of α-amido p-tolylsulfones were prepared from aromatic as well as aliphatic aldehydes for the synthesis of α-amino nitriles.  相似文献   

5.
A novel methodology leading to the synthesis of (+)-triacetoxygoniotriol 2 from d-glucose is described. Construction of the core six-membered α,β-unsaturated lactone moiety involved ring closing metathesis (RCM) followed by a PCC oxidation. Later exploiting the pseudo-symmetry of d-glucose three other diastereomers of triacetoxygoniotriol were synthesized using the developed methodology.  相似文献   

6.
《Tetrahedron letters》1986,27(31):3599-3602
Nucleoside 5′-0-(1-thiodi-) and triphosphates can be obtained in yields of up to 45% directly from the nucleosides. Their diastereomers can be separated by preparative reversed phase chromatography.  相似文献   

7.
Diastereoselective aza-Diels-Alder (aza-DA) reactions of ethyl (S)-N-(tert-butanesulfinyl)iminoacetate (2a) and ethyl (S)-N-(p-toluenesulfinyl)iminoacetate (2b) with different dienes including activated, non-activated, cyclic, and acyclic dienes in the presence of Lewis acids are described. Reactions with 2a were found to be more selective. Reactions of unactivated dienes (acyclic and cyclic) with stoichiometric amounts of TMSOTf as Lewis acid afforded the aza-DA adducts in modest yields and in diastereoselectivities up to 99%. A strong preference for Re-approach was observed for 2a. Cyclic dienes gave the exo adducts as major products. For the aza-DA reaction with activated Danishefsky type dienes poor diastereoselectivities were observed. In these cases, the best results were obtained using stoichiometric amounts of BF3·Et2O as Lewis acid (up to 69% de, 76% yield). The absolute configurations of six of the addition products were established by chemical correlation with known compounds. Acidic cleavage of the sulfinyl group occurred without racemization to optically active non-proteinogenic α-amino acid ethyl esters.  相似文献   

8.
《Tetrahedron: Asymmetry》1998,9(20):3611-3614
Diastereoselective alkylation of ethyl (5S)-3,6-diethoxy-2,5-dihydro-5-isopropyl-2-pyrazinecarboxylate (5S)-3 with alkyl halides was investigated by using NaH and n-BuLi. These alkylated products (2R,5S)-4bd were converted to the corresponding α-alkylated serines (S)-6bd.  相似文献   

9.
An organocatalytic sequential α-amination/Grignard addition reaction of aliphatic aldehydes is reported. The synthetically useful anti-vicinal amino alcohol derivatives were obtained in high yields and with high stereoselectivities. These derivatives could be easily transformed into oxazolidinones.  相似文献   

10.
A simple transition-metal-free protocol for the synthesis of indoles has been developed using aryne cycloaddition. The in situ-generated arynes couple with α-amino ketones through a one-step N-arylation–nucleophilic addition process under mild conditions and efficiently produce multisubstituted N-arylindoles.  相似文献   

11.
Highly enantiomerically enriched N-protected α-amino acids can be easily prepared from optically pure N-(tert-butanesulfinyl)imines by a four-step sequence involving: diastereoselective addition of a triorganozincate to the imine, removal of the sulfinyl group, benzoylation of the nitrogen atom of the obtained primary amine and oxidation of one of the substituents on the carbon atom α to the nitrogen. Using the same configuration in the sulfinyl chiral auxiliary, amino acids with the (R) or the (S) configuration can be prepared by choosing the proper combination of imine and organozincate. α,α-Disubstituted α-amino esters with high optical purity can also be prepared by the diastereoselective addition of trialkylzincates to α-imino esters.  相似文献   

12.
Investigation of the reaction of α-thioamides, α-esters and α-nitriles with NBS and NCS is described. The scope of this stereoselective oxidative transformation to the β-haloacrylamides, β-acrylates and β-acrylonitriles has been determined. A mechanistic rationale to explain the observed differences in reactivity between the amide, ester and nitrile series is proposed.  相似文献   

13.
An efficient and practical electrophilic amination method that allows the preparation of useful quaternary carbon-containing α-aminoketones was developed. The reaction proceeds regiospecifically via a samarium enolate intermediate at room temperature in the presence of mild reducing agent SmI2. Unlike the most reported lithium enolate cases, this new amination method does not require the use of strong base such as BuLi or LDA.  相似文献   

14.
15.
Roman B?aszczyk 《Tetrahedron》2010,66(52):9840-7546
An efficient one-pot synthesis of secondary N-carbamate protected syn-β-amino-α-nitroalkanephosphonates using diethyl nitromethanephosphonate and N-Boc or N-Cbz imines, generated in situ from stable N-Boc or N-Cbz α-aminoalkyl-p-tolylsulfones has been developed under PTC conditions. A model enantioselective version of this reaction is also described. Enantioselectivity up to 67% ee is achieved using a chiral thiourea catalyst derived from a cinchona alkaloid. Completely stereoselective conversion of the title compounds into partially N-carbamate protected syn-1,2-diaminoalkanephosphonates has also been elaborated.  相似文献   

16.
4-Phosphoranylidene-5(4H)-oxazolones 1 undergo hydrolysis in THF in the presence of HBF4 at room temperature to give N-acyl-α-triphenylphosphonioglycines 3 (R2 = H) in very good yields. 4-Alkyl-4-triphenylphosphonio-5(4H)-oxazolones 2 react with water in CH2Cl2/THF solution without any acidic catalyst at 0-5 °C in a few days yielding N-acyl-α-triphenylphosphonio-α-amino acids 3 (R2 = Me) or α-(N-acylamino)alkyltriphenylphosphonium salt 4 (R2 = CH2OMe). α-Triphenylphosphonio-α-amino acids 3, on heating up to 105-115 °C under reduced pressure (5 mmHg) or on treatment with diisopropylethylamine in CH2Cl2 at 20 °C undergo decarboxylation to give the corresponding α-(N-acylamino)alkyltriphenylphosphonium salts 4, usually in very good yields.  相似文献   

17.
A novel photocatalytic cross dehydrogenative coupling reaction of N-aryl glycine esters with N-substituted anilines has been developed. The reaction proceeds effectively using methylene blue as a photocatalyst under visible light irradiation without any metal, chemical oxidant or additive. A variety of α-aryl α-amino derivatives were prepared in moderate to excellent yields with a high para-regioselectivity.  相似文献   

18.
An efficient approach to the synthesis of 3-azabicyclo[3.3.0]octanes and 3-azabicyclo[4.3.0]nonanes by 2nd generation palladium-catalyzed cycloalkenylation is described. Additionally, this reaction is used for the diastereoselective total synthesis of (±)-α-skytanthine.  相似文献   

19.
A straightforward procedure for the preparation of N-quinoxaline-indoles is presented. A base-catalyzed one-pot addition of indoles to a preformed α-iminoketone proceeds on the N-1 indole and the subsequent adduct undergoes an acid-mediated deprotection of an internal amino nucleophile, intramolecular cyclization, and final oxidation generating N-1-quinoxaline-indoles in good yield.  相似文献   

20.
Chiral N-phosphonyl imines attached by 1-naphthyl group were found to react with lithium malonate enolates smoothly to give chiral β-aminomalonates. Good yields and excellent diastereoselectivity were achieved for sixteen examples. The chiral auxiliary can be readily removed by treating with trifluoroacetic acid (TFA) to give free amino malonates. The absolute structure has been unambiguously determined by converting one of the products into an authentic sample.  相似文献   

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