Search results for "SELECTIVITY"
showing 10 items of 1148 documents
Novel strategy for the synthesis of fluorinated β-amino acid derivatives from Δ2-oxazolines
2001
Abstract Racemic and chiral non-racemic β-fluoroalkyl-β-amino acid derivatives have been prepared in two steps starting from 2-alkyl-Δ2-oxazolines and fluorinated imidoyl chlorides. Subsequent chemoselective reduction of the C-masked β-enamino acid derivatives initially formed provided the target β-amino acids. The process takes place with total chemoselectivity, high yields and satisfactory diastereoselectivity.
Dianions of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Juvocimene I
1996
Abstract Juvocimene I is prepared by a non ambiguous synthesis based on the regioselective alkylation of 4-methylhexa-2,4-dienoic acid, and Wittig olefination of the aldehyde corresponding to the alkylated acid.
ChemInform Abstract: Novel Strategy for the Synthesis of Fluorinated β-Amino Acid Derivatives from Δ2-Oxazolines.
2010
Abstract Racemic and chiral non-racemic β-fluoroalkyl-β-amino acid derivatives have been prepared in two steps starting from 2-alkyl-Δ2-oxazolines and fluorinated imidoyl chlorides. Subsequent chemoselective reduction of the C-masked β-enamino acid derivatives initially formed provided the target β-amino acids. The process takes place with total chemoselectivity, high yields and satisfactory diastereoselectivity.
ChemInform Abstract: Dianions of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Juvocimene I.
2010
Abstract Juvocimene I is prepared by a non ambiguous synthesis based on the regioselective alkylation of 4-methylhexa-2,4-dienoic acid, and Wittig olefination of the aldehyde corresponding to the alkylated acid.
ChemInform Abstract: Efficient Stereoselective Synthesis of Boron L-amino Acid Derivatives Using Wittig and Borylation Reactions
2015
The stereoselective synthesis of a new classes of boronato- or trifluoroborato aminoacids and peptides was described using Wittig and C-H iridium borylation as key reactions. A trifluoroborato-thio...
Arabinosylamine in Asymmetric Syntheses of Chiral Piperidine Alkaloids.
2004
The stereodifferentiating potential of arabinosyl aldimines was utilized in stereoselective syntheses of 2-substituted dehydropiperidinones and their further transformation to 2,6-cis-substituted piperidinones. The absolute configuration was proven by X-ray analysis and by the synthesis of the enantiomerically pure alkaloid (+)-dihydropinidine. The presented method offers the possibility to synthesize piperidine derivatives enantiomeric to those obtained by the application of the corresponding galactosylamine auxiliary.
ChemInform Abstract: A Stereoselective Synthesis of (+)-Malyngolide via a Ring-Closing Olefin Metathesis.
2000
Abstract A very short and stereoselective synthesis of the non-natural enantiomer of malyngolide from l -erythrulose is described. Key features of the synthesis are the Felkin–Anh diastereoselective allylation of a polyoxygenated ketone and the allylation/metathesis/allylic oxidation protocol recently described by our group.
Regioselective Annulation of Alicyclic−Aromatic Dienes with 3-Halo-3-cyclobutene-1,2-diones. Synthesis of Annulated α-Halobenzocyclobutenones1
1998
4-(1-Cycloalken-1-yl)-1,2-dialkoxybenzenes 8, 10, and 11 and 5-(1-cycloalken-1-yl)-1,3-benzodioxoles 12−15 react with the semisquaric halides 5a and 5b in a dehydrative annulation process to give the annulated α-halobenzocyclobutenones 9a,b and 16a,b−21a,b in poor to good yields (20−76%). The reaction failed with alicyclic−aromatic dienes having no or only one alkoxy group in the benzene ring. The dehydrative annulation process could be extended to 4-(3,4-dimethoxyphenyl)-1,2-dihydronaphthalene (24), affording the highly annulated α-chlorobenzocyclobutenone 25 in 50% yield. In the case of 5-(1-cyclobuten-1-yl)-1,3-benzodioxole (22), reaction with the semisquaric halides 5a,b yielded the dic…
Stereoselective Synthesis of 8,12-Furanoeudesmanes from Santonin. Absolute Stereochemistry of Natural Furanoeudesma-1,3-diene and Tubipofurane.
1996
Ketobutenolide 3, easily obtained from santonin (1), has been transformed into two natural furanoeudesmanes 4 and 5, isolated from Commiphora molmol and Tubipora musica, respectively. trans- And cis-decalin systems were obtained by stereoselective reduction of the C(4)-C(5) double bond in 3 in the following way: hydrogenation of 3 over Pd/C followed by acidic treatment gave the cis isomer 10 as the major product; selective hydrogenation of the C(1)-C(2) double bond with the Wilkinson's catalyst followed by reduction with NaTeH yielded mainly the trans isomer 9. Compounds 9 and 10 were transformed into 4 and 5 in parallel sequences. Optical rotation and CD measurements of the synthetic produ…
ChemInform Abstract: Synthesis of α-Fucosyl Glycosides and Disaccharides Using 4- Methoxybenzyl (Mpm) Protected Fucosyl Donors.
2010
The 4-methoxybenzyl (Mpm) group removable by selective oxidation was applied as a nonneighbouring-group-active protection of fucose hydroxy functions in the stereoselective synthesis of α-fucosides of acceptors containing double bonds sensitive to hydrogenation. With this aim, the synthesis of the α-fucosyl chloride (4) carrying the acidsensitive Mpm protection was elaborated.