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1.
Botman PN Dommerholt FJ de Gelder R Broxterman QB Schoemaker HE Rutjes FP Blaauw RH 《Organic letters》2004,6(26):4941-4944
[reaction: see text] Herein, we report a diastereoselective synthesis of the natural product (2S,5R)-5-hydroxypipecolic acid and 6-substituted derivatives thereof. The key step in the synthetic sequence is a novel highly diastereoselective epoxidation reaction of an enantiomerically pure cyclic enamide intermediate. 相似文献
2.
《Tetrahedron: Asymmetry》2006,17(17):2479-2486
An efficient diastereoselective synthesis of cis- and trans-5-hydroxy-(2S)-N-benzyloxycarbonyl pipecolic acids, starting from trans-4-hydroxy-l-proline is described. The key synthetic strategies involve the regioisomeric ring expansion of keto ester 8 and diastereoselective reduction of ketone 11 in high selectivity and yield. 相似文献
3.
《Tetrahedron: Asymmetry》2001,12(22):3173-3183
The sulfoxide-mediated diastereoselective Michael reaction of homochiral α-sulfinylketimines 1a–d and β-substituted ene esters 2a–d (Hua's reaction) was explored. Straightforward cyclization of the open-chain adducts take place under the reaction conditions to provide the 4-substituted 5-(p-tolylsulfinyl)-5,6-dehydropiperidin-2-ones 3 and 7–12, whose stereochemistry is formed in the prior step. Furthermore, the role of the metal ion of the aza-enolate reagents and the steric demands of the O-alkyl ester group have been examined. It seems that the anti-diastereoselectivity depends on metal chelation by the oxygen of the ester as well as the oxygen of the sulfinyl group and the nitrogen in the aza-enolate ((Z)-configuration). In addition, the synthesis of methyl l-(2S,4S)-4-methyl-6-oxopipecolate has been achieved from the suitably functionalized 2-sulfinylketimine 1a (five steps; overall yield: 53–65%). 相似文献
4.
Tsunetoshi Honma Yukio Tada Ikuo Adachi Kikuo Igarashi 《Journal of heterocyclic chemistry》1989,26(3):629-634
(2S,5S)-3-Alkylpyrrolidine-2, 5-dicarboxylic acid derivatives I were stereoselectively synthesized by means of an efficient method starting from L-aspartic acid ( 1 ). Dieckmann reaction of 4-benzyl 1-t-butyl N-t-butyl-oxycarbonyl-N-ethoxycarbonylmethyl-L-aspartate ( 4 ) provided product 5 which consisted of a mixture of (2S,5S)- and (2R,5S)-1-t-butyloxycarbonyl-3-oxopyrrolidine-2, 5-dicarboxylates in a ratio of 95:5. Treating 1-t-butyl 6-ethyl 2-L-(t-butyloxycarbonyl)anuno-5-diazo-4-oxoadipate ( 8 ), prepared from 1 , with rhodium(II) acetate dimer also afforded a good yield of 5 . The Wittig reaction of 5 , followed by catalytic hydrogenation and then deprotection provided compound I . 相似文献
5.
The reaction of piperdin-2-ones with a 2-bromobenzyl substituent in the 5-position in the presence of a palladium catalyst leads to biaryl compounds. Their formation can be explained via initial C-H insertion of the aryl palladium species into the allylic C-H bond of the piperidinone. This eventually leads to a metallacycle containing Pd(II) that inserts another aryl bromide, promoting the formation of the biaryl bond. 相似文献
6.
Wishka DG Bédard M Brighty KE Buzon RA Farley KA Fichtner MW Kauffman GS Kooistra J Lewis JG O'Dowd H Samardjiev IJ Samas B Yalamanchi G Noe MC 《The Journal of organic chemistry》2011,76(6):1937-1940
To facilitate a drug discovery project, we needed to develop a robust asymmetric synthesis of (2S,5S)-5-substituted-azepane-2-carboxylate derivatives. Two key requirements for the synthesis were flexibility for elaboration at C5 and suitability for large scale preparation. To this end we have successfully developed a scalable asymmetric synthesis of these derivatives that starts with known hydroxy-ketone 8. The key step features an oxidative cleavage of aza-bicyclo[3.2.2]nonene 14, which simultaneously generates the C2 and C5 substituents in a stereoselective manner. 相似文献
7.
Xinrong Tian Dominic P. Suarez William Hoi Hong Li Allison K. McSherry Robert M. Sanchez Michael L. Moore Jeffrey M. Axten 《Tetrahedron letters》2019,60(49):151312
We describe an efficient synthesis of 2,4-substituted pyrido[4,3-d]pyrimidin-5(6H)-ones, which involves the acid-promoted cyclization of cyano enamine 15 to afford 2,4-bis(methylthio)pyrido[4,3-d]pyrimidin-5(6H)-one 17 as a key intermediate. Selective displacement of the 4-methylthio group by a wide range of anilines followed by oxidation of the 2-methylthio group and subsequent substitution by amines enabled the synthesis of a variety of 2,4-disubstituted pyrido[4,3-d]pyrimidin-5(6H)-ones. 相似文献
8.
9.
《Tetrahedron letters》1987,28(20):2299-2300
10.
《Tetrahedron: Asymmetry》2003,14(8):1063-1072
An efficient and easy one-pot reaction from readily available racemic 2-substituted cyclobutanones gave, by means of asymmetric Strecker synthesis in the presence of an amine chiral auxiliary, two major aminonitriles with excellent diastereoselectivity. After separation, the major cis-aminonitriles were hydrolysed and hydrogenolysed to lead for the first time to pure non-racemic (+)-1-amino-2-isopropylcyclobutanecarboxylic acid (ACBC) and its antipode. 相似文献
11.
Shklyaev Yu. V. Nifontov Yu. V. Shashkov A. S. Firgang S. I. 《Russian Chemical Bulletin》2002,51(12):2234-2237
Reactions between p-methylanisole, isobutyraldehyde, and nitriles (acetonitrile, methyl thiocyanate, or ethyl cyanoacetate) in conc. H2SO4 yield 1-substituted (R,S)-8-(2-methoxy-5-methylphenyl)-3,3,9-trimethyl-2-azaspiro[4.5]deca-1,7-dien-6-ones. 相似文献
12.
Razieh Doostmohammadi Malek Taher Maghsoodlou Nourallah Hazeri Sayyed Mostafa Habibi-Khorassani 《中国化学快报》2013,24(10):901-903
A facile one-pot synthesis of 3,4,5-substituted furan-2(5H)-one derivatives from a three-component reaction of aniline derivatives, dialkylacetylenedicarboxylates and aromatic aldehydes under mild conditions using tetra-n-butylammonium bisulfate as a catalyst has been developed. 相似文献
13.
A convenient approach for the preparation of (2S,3R,4R,5S,6R)-2-(3-(4-ethylbenzyl)-4-chlorophenyl)-6-(hydroxymethyl)- tetrahydro-2H-pyran-3,4,5-triol I is developed. The target compound via four steps is synthesized from 4-bromo-2-(bromomethyl)- 1-chlorobenzene and the isomers of undesired ortho-products were avoided during the preparation. 相似文献
14.
Wei ZL Sakamuri S Petukhov PA George C Lewin NE Blumberg PM Kozikowski AP 《Organic letters》2002,4(13):2169-2172
[structures: see text] Both (2S,5R,6R)- and (2S,5R,6S)-6-hydroxy-8-(1-decynyl)benzolactam-V8 were designed and synthesized as PKC modulators. Biological assays reveal the (6R)-ligand to be 20-fold more potent than its (6S)-counterpart in binding to PKC alpha. 相似文献
15.
《Tetrahedron: Asymmetry》2007,18(4):513-519
Total synthesis of (4R,5S,6E,14S)- and (4R,5S,6E,14R)-cystothiazoles F 3 was achieved from the chiral bithiazole-type primary alcohols [(S)- and (R)-4-ethoxycarbonyl-2′-(1-hydroxymethylethyl)-2,4′-bithiazoles 8], which were obtained based on the enzymatic resolution of racemic alcohol 8 and its acetate 9. From a direct comparison by means of chiral HPLC between natural cystothiazole F 3 and synthetic compounds [(4R,5S,6E,14S)- and (4R,5S,6E,14R)-cystothiazoles 3], natural cystothiazole F 3 was found to be a 33:67 diastereomeric mixture [(4R,5S,6E,14S)-3:(4R,5S,6E,14R)-3 = 33:67]. 相似文献
16.
Anastasia A. Fesenko 《Tetrahedron letters》2007,48(48):8420-8423
A three-stage diastereoselective synthesis of (4R∗,5R∗,6S∗)-5-mercapto-4-methyl-6-phenylhexahydropyrimidin-2-one has been developed. The first stage involves the formation of 4-hydroxy-5-(4-methoxybenzylthio)-4-methyl-6-phenylhexahydropyrimidin-2-one by the reaction of N-[(phenyl)(tosyl)methyl]urea with the sodium enolate of 1-(4-methoxybenzylthio)propan-2-one. Reduction of the obtained compound by NaBH4-CF3COOH and removal of the p-methoxybenzyl protecting group results in the target compound. 相似文献
17.
A variety of diolefinic hydrazides (1) have been assembled in a highly diastereoselective manner by addition of allyllithium to chiral SAMP hydrazones followed by N-acylation with acryloyl chloride. Substrates 1 undergo ring-closing metathesis to give the cyclic enehydrazides (5) which can be easily converted into virtually enantiopure 6-alkyl- or 6-arylpiperidin-2-ones (7). The versatility of this hydrazone addition-RCM protocol has been further exemplified by the conversion of the unsaturated heterocycle 5b into the piperidine alkaloid (S)-(+)-coniine. 相似文献
18.
Amalia M. Estévez Raquel G. Soengas José M. Otero Juan C. Estévez Robert J. Nash Ramón J. Estévez 《Tetrahedron: Asymmetry》2010,21(1):21-26
A divergent synthesis of the two novel polyhydroxylated azepanes (2R,3R,4R,5R,6R)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol and (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol from d-mannose is described. The method involves a Henry reaction between dimethyl-tert-butylsilyl 2,3-O-isopropylidene-α-d-lyxo-pentodialdo-1,4-furanoside and 2-nitroethanol followed by a reductive ring closure of the resulting epimeric nitro aldols. Glycosidase inhibition tests showed that (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol exhibits a weak but selective inhibition against α-l-fucosides. 相似文献
19.
20.
Racemic 8-ethoxy-2-(4-fluorophenyl)-3-nitro-2H-chromene (S14161) was recently identified as a potent inhibitor of phosphoinositide 3-kinase (PI3K). In order to investigate the effects of its two enantiomers on tumor cell lines, we designed a novel synthesis for (R)-S14161 and (S)-S14161 using a chemical resolution and derivation strategy. The readily available 3-(tert-butyldimethylsilyloxy)-salicylaldehyde underwent a tandem oxa-Michael–Henry reaction with trans-4-fluoro-β-nitrostyrene in the presence of a catalytic amount of l-proline and triethylamine to give the 3-nitro-2H-chromene. Upon removal of the TBS protecting group, the resolution of the resulting racemic 2-(4-fluorophenyl)-8-hydroxy-3-nitro-2H-chromene was achieved via diastereomeric ester formation using (S)-(+)-α-methoxyphenylacetic acid as the derivatizing agent, followed by aminolysis. Finally, the ethyl ether formation of each enantiomer furnished (R)-S14161 and (S)-S14161 in enantiomerically pure forms. The absolute configurations of these chiral molecules were determined by a circular dichroism method. The two enantiomers showed no marked differences in inhibition of growth of human myeloma LP1 and OPM-2 cells. 相似文献