... 1 Eusebio Juaristi* and J. Daniel Reyna Departamento de QuImica del Centro de Investigacion y... more ... 1 Eusebio Juaristi* and J. Daniel Reyna Departamento de QuImica del Centro de Investigacion y de Estudios Avanzados del Instituto Po1itcnico Nacional, Apartado Postal 14740 ... Chem. Abstr., 19S9, 53, 1250 f. 7. For recent examples see: Sundberg, RJ; Laurino, JP, J. Org. ...
A variable-temperature NMR study of (cis-4-methylcyclohexyl)methyl sulfide (1), sulfoxide (2), an... more A variable-temperature NMR study of (cis-4-methylcyclohexyl)methyl sulfide (1), sulfoxide (2), and sulfone (3), as well as (cis-4-methylcyclohexyl)phenyl sulfide (4), sulfoxide (5), and sulfone (6) allowed determination of the thermodynamic parameters, DeltaH degrees and DeltaS degrees, for the title groups. Reproduction of the experimental results with Allinger's MM3 program was successfully accomplished in the case of the sulfoxide and sulfide groups. Nevertheless, modification of the original force field torsional parameters was required in order to adequately reproduce the experimentally observed behavior of the sulfonyl derivatives. Rationalization of the enthalpic and entropic contributions to DeltaG degrees [S(O)(n)()R, n = 0, 1, 2; R = CH(3), Ph] is advanced in terms of the steric characteristics of these sulfur-containing groups and the resulting rotameric populations in the axial and equatorial monosubstituted cyclohexanes.
The reactivity of N-tert-butyloxycarbonyl-N-carboxyanhydrides derived from β-alanine, (S)-β(3)-ho... more The reactivity of N-tert-butyloxycarbonyl-N-carboxyanhydrides derived from β-alanine, (S)-β(3)-homophenylglycine, and (S)-β(3)-carboxyhomoglycine with different α- and β-amino ester hydrochlorides was examined under ball-milling activation. In particular, good to excellent yields of several relevant α,β- and β,β-dipeptides were obtained. An illustrative application of this methodology consisted in the high-yield synthesis of the mammalian α,β-dipeptide N-Boc-l-carnosine-OMe.
Eusebio Juaristi* and J. Samuel Cruz-SBnchez Departamento de Quimica, Centro de Investigacidn y d... more Eusebio Juaristi* and J. Samuel Cruz-SBnchez Departamento de Quimica, Centro de Investigacidn y de Estudios Auanzados del IPN, Apdo. Postal 14-740, 07000 MGwico D F., Mexico Received January 25, 1988 ... The synthesis of the title compound (6), an interesting subject for the ...
The preparation of four new stereoisomeric 1-carbobenzyloxy-2-tert-butyl-3-(α-methylbenzyl)-1,3-i... more The preparation of four new stereoisomeric 1-carbobenzyloxy-2-tert-butyl-3-(α-methylbenzyl)-1,3-imidazolidin-4-ones is described. Alkylation of the lithium enolates of these chiral glycine derivatives proceeds with high diastereoselectivity. In particular, the reaction of the unlike isomers, (2R, 1′S)- and (2S, 1′R)-7, afforded the desired phosphorylated products 9 with ≥ 98% diastereoselectivity. Hydrolysis of the alkylated products proceeds under relatively mild conditions to give enantiomerically pure
A high-yield, five-step synthesis of novel enantiomerically pure cis- and trans-N-(propionyl)-hex... more A high-yield, five-step synthesis of novel enantiomerically pure cis- and trans-N-(propionyl)-hexahydrobenzoxazolidin-2-ones5a-d from cyclohexene oxide and (S)-α-methylbenzylamine is described. The highly diastereoselective benzylation of 5b is also described.
The reaction of 2-phenyl-l, 3-dithianyllithium (1-Li) with 4-tert-butylcyclohexanone in cyclohexa... more The reaction of 2-phenyl-l, 3-dithianyllithium (1-Li) with 4-tert-butylcyclohexanone in cyclohexane and tetrahydrofuran may proceed either with kinetic or thermodynamic control. In the latter case carbinol formation involves exclusively equatorial attack. In contrast, only ...
Introduction. - In addition to their fundamental biochemical and physiological signif-icance6), a... more Introduction. - In addition to their fundamental biochemical and physiological signif-icance6), amino acids are important in human and animal nutrition and as flavorings, taste enhancers, and sweeteners [l]. Both natural7) and unnatural amino acids are also ...
The efficient palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of (2S)-isopropyl-5-iodo... more The efficient palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of (2S)-isopropyl-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-one with, arylethynyl-, heteroarylethynyl-, and alkylethynyltrifluoroborate salts is reported. The standard protocol was evaluated and optimized in order to gain access to suitable precursors of enantiopure 2-substituted β-amino acids. The scope and limitations of this methodology are discussed.
... 1 Eusebio Juaristi* and J. Daniel Reyna Departamento de QuImica del Centro de Investigacion y... more ... 1 Eusebio Juaristi* and J. Daniel Reyna Departamento de QuImica del Centro de Investigacion y de Estudios Avanzados del Instituto Po1itcnico Nacional, Apartado Postal 14740 ... Chem. Abstr., 19S9, 53, 1250 f. 7. For recent examples see: Sundberg, RJ; Laurino, JP, J. Org. ...
A variable-temperature NMR study of (cis-4-methylcyclohexyl)methyl sulfide (1), sulfoxide (2), an... more A variable-temperature NMR study of (cis-4-methylcyclohexyl)methyl sulfide (1), sulfoxide (2), and sulfone (3), as well as (cis-4-methylcyclohexyl)phenyl sulfide (4), sulfoxide (5), and sulfone (6) allowed determination of the thermodynamic parameters, DeltaH degrees and DeltaS degrees, for the title groups. Reproduction of the experimental results with Allinger's MM3 program was successfully accomplished in the case of the sulfoxide and sulfide groups. Nevertheless, modification of the original force field torsional parameters was required in order to adequately reproduce the experimentally observed behavior of the sulfonyl derivatives. Rationalization of the enthalpic and entropic contributions to DeltaG degrees [S(O)(n)()R, n = 0, 1, 2; R = CH(3), Ph] is advanced in terms of the steric characteristics of these sulfur-containing groups and the resulting rotameric populations in the axial and equatorial monosubstituted cyclohexanes.
The reactivity of N-tert-butyloxycarbonyl-N-carboxyanhydrides derived from β-alanine, (S)-β(3)-ho... more The reactivity of N-tert-butyloxycarbonyl-N-carboxyanhydrides derived from β-alanine, (S)-β(3)-homophenylglycine, and (S)-β(3)-carboxyhomoglycine with different α- and β-amino ester hydrochlorides was examined under ball-milling activation. In particular, good to excellent yields of several relevant α,β- and β,β-dipeptides were obtained. An illustrative application of this methodology consisted in the high-yield synthesis of the mammalian α,β-dipeptide N-Boc-l-carnosine-OMe.
Eusebio Juaristi* and J. Samuel Cruz-SBnchez Departamento de Quimica, Centro de Investigacidn y d... more Eusebio Juaristi* and J. Samuel Cruz-SBnchez Departamento de Quimica, Centro de Investigacidn y de Estudios Auanzados del IPN, Apdo. Postal 14-740, 07000 MGwico D F., Mexico Received January 25, 1988 ... The synthesis of the title compound (6), an interesting subject for the ...
The preparation of four new stereoisomeric 1-carbobenzyloxy-2-tert-butyl-3-(α-methylbenzyl)-1,3-i... more The preparation of four new stereoisomeric 1-carbobenzyloxy-2-tert-butyl-3-(α-methylbenzyl)-1,3-imidazolidin-4-ones is described. Alkylation of the lithium enolates of these chiral glycine derivatives proceeds with high diastereoselectivity. In particular, the reaction of the unlike isomers, (2R, 1′S)- and (2S, 1′R)-7, afforded the desired phosphorylated products 9 with ≥ 98% diastereoselectivity. Hydrolysis of the alkylated products proceeds under relatively mild conditions to give enantiomerically pure
A high-yield, five-step synthesis of novel enantiomerically pure cis- and trans-N-(propionyl)-hex... more A high-yield, five-step synthesis of novel enantiomerically pure cis- and trans-N-(propionyl)-hexahydrobenzoxazolidin-2-ones5a-d from cyclohexene oxide and (S)-α-methylbenzylamine is described. The highly diastereoselective benzylation of 5b is also described.
The reaction of 2-phenyl-l, 3-dithianyllithium (1-Li) with 4-tert-butylcyclohexanone in cyclohexa... more The reaction of 2-phenyl-l, 3-dithianyllithium (1-Li) with 4-tert-butylcyclohexanone in cyclohexane and tetrahydrofuran may proceed either with kinetic or thermodynamic control. In the latter case carbinol formation involves exclusively equatorial attack. In contrast, only ...
Introduction. - In addition to their fundamental biochemical and physiological signif-icance6), a... more Introduction. - In addition to their fundamental biochemical and physiological signif-icance6), amino acids are important in human and animal nutrition and as flavorings, taste enhancers, and sweeteners [l]. Both natural7) and unnatural amino acids are also ...
The efficient palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of (2S)-isopropyl-5-iodo... more The efficient palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of (2S)-isopropyl-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-one with, arylethynyl-, heteroarylethynyl-, and alkylethynyltrifluoroborate salts is reported. The standard protocol was evaluated and optimized in order to gain access to suitable precursors of enantiopure 2-substituted β-amino acids. The scope and limitations of this methodology are discussed.
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