Catalytic Asymmetric Syntheses of Tyrosine Surrogates

Han, Xiaojun; Civiello, Rita L.; Fang, Haiquang; Wu, Dedong; Gao, Qi; Chaturvedula, Prasad V.; Macor, John E.; Dubowchik, Gene M.

doi:10.1021/jo801577t

Cited by 19 publications

(11 citation statements)

References 35 publications

(35 reference statements)

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“…Use of Rh-catalysed asymmetric hydrogenation in an enantioselective synthesis of the benzoxalone derivative 12, a tyrosine mimic, has been reported by researchers at Bristol-Myers Squibb. 63 The cornerstone of the synthetic sequence was the enantioselective hydrogenation of the b-aryl a-(acylamino)acrylate 10 using Burk's catalyst, 64 derived from the milestone ligand (R,R)-Et-DUPHOS. The N-Cbz-protected acrylate 10 was then efficiently reduced under mild reaction conditions (rt, 4 bar H 2 ) by using 1.0 mol% of rhodium complex and working in an optimised mixture of solvents (1 : 1 MeOH/DCM).…”

Section: Enantioselective Hydrogenation Of Acrylate Derivativesmentioning

confidence: 99%

Rhodium-catalysed asymmetric hydrogenation as a valuable synthetic tool for the preparation of chiral drugs

2013

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During the last few decades, rhodium-catalysed asymmetric hydrogenation of diverse alkene classes has emerged as a powerful synthetic tool in the pharmaceutical industry, contributing to the manufacturing of chiral drugs, recent drug candidates for clinical trials, and major synthetic precursors of drugs. Numerous efficient chiral rhodium complexes, most of which are derived from enantiopure phosphorus ligands, have been employed for the preparation of chiral drugs and intermediates thereof. This review article is intended to provide an updated overview of the most striking contributions in this field, organised according to substrate class: acrylate derivatives, itaconate derivatives, α-substituted enamides, α-arylenol acetates, and minimally functionalised olefins.

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Section: Enantioselective Hydrogenation Of Acrylate Derivativesmentioning

confidence: 99%

Rhodium-catalysed asymmetric hydrogenation as a valuable synthetic tool for the preparation of chiral drugs

2013

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“…The methylene group attached to the iodide is essentially first-order. 47 A screen of published spectra revealed that 2-trimethylsilylethanesulfonyl chloride 9, 48 the precursor for the commonly used SES protecting group, and the corresponding N-SES derivatives both display second-order AA¢XX¢ spectra. 49 Clearly, the large sulfonyl combined with the large trimethylsilyl groups are favouring the anti-conformers and extenuating the differences in vicinal coupling constants leading to strong second-order behaviour.…”

Section: Resultsmentioning

confidence: 99%

Second-order NMR spectra at high field of common organic functional groups

Stevenson

2011

Org. Biomol. Chem.

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The proton NMR spectra of aryl n-propyl sulfides gave rise to what may appear to be first-order proton NMR spectra. Upon oxidation to the corresponding sulfone, the spectra changed appearance dramatically and were clearly second-order. A detailed analysis of these second-order spectra, in the sulfone series, provided vicinal coupling constants which indicated that these compounds had a moderate preference for the anti-conformer, reflecting the much greater size of the sulfone over the sulfide. It also emerged, from this study, that the criterion for observing large second-order effects in the proton NMR spectra of 1,2-disubstituted ethanes was that the difference in vicinal coupling constants must be large and the difference in geminal coupling constants must be small. n-Propyl triphenylphosphonium bromide and 2-trimethylsilylethanesulfonyl chloride, and derivatives thereof, also exhibited second-order spectra, again due to the bulky substituents. Since these spectra are second-order due to magnetic nonequivalence of the nuclei in question, not chemical shifts, the proton spectra are perpetually second-order and can never be rendered first-order by using higher field NMR spectrometers.

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“…This compound was prepared in four steps by bromination of 3-nitrobenzoic acid (12), [25] reduction of the carboxylic acid, [26] protection of the resulting alcohol as a MOM ether, [27] and a Bechamp reduction of the nitro group (Scheme 6). [28] The overall yield was 61 % over four steps.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Isomerization Studies of Cyclotrisazobiphenyl

Reuter

Wegner

2011

Chemistry A European J

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We report an efficient synthesis of cyclotris[(E)-3'-(biphenyl-3-yldiazenyl)] compounds (CTBs). An unsubstituted CTB molecule is accessible in four steps in 10% yield overall, whereas a hexa(methoxymethyl ether) CTB analogue was prepared in nine steps (26% yield). The final macrocyclization step was accomplished in up to 80% yield by using a metal-template effect. Furthermore, the photochromic properties were investigated, and all four isomers were detected and characterized by NMR spectroscopy. A strong influence from the solvent and the irradiation wavelength on the switching process was observed. Irradiation in pyridine yielded the highest amount of the all-Z isomer in the photostationary state. For a full conversion to the all-E isomer, the reaction has to be heated to 45 °C. The isomerization to the all-E isomer is slow at room temperature, with a half-life time of the all-Z isomer of more than nine days in dimethyl sulfoxide (DMSO). Conditions were established to access each possible isomer as the major component in the photostationary state.

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Catalytic Asymmetric Syntheses of Tyrosine Surrogates

Cited by 19 publications

References 35 publications

Rhodium-catalysed asymmetric hydrogenation as a valuable synthetic tool for the preparation of chiral drugs

Rhodium-catalysed asymmetric hydrogenation as a valuable synthetic tool for the preparation of chiral drugs

Second-order NMR spectra at high field of common organic functional groups

Synthesis and Isomerization Studies of Cyclotrisazobiphenyl

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