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321-97-1Relevant academic research and scientific papers
Evaluation of the Edman degradation product of vancomycin bonded to core-shell particles as a new HPLC chiral stationary phase
Hellinghausen, Garrett,Lopez, Diego A.,Lee, Jauh T.,Wang, Yadi,Weatherly, Choyce A.,Portillo, Abiud E.,Berthod, Alain,Armstrong, Daniel W.
, p. 1067 - 1078 (2018/08/01)
A modified macrocyclic glycopeptide-based chiral stationary phase (CSP), prepared via Edman degradation of vancomycin, was evaluated as a chiral selector for the first time. Its applicability was compared with other macrocyclic glycopeptide-based CSPs: TeicoShell and VancoShell. In addition, another modified macrocyclic glycopeptide-based CSP, NicoShell, was further examined. Initial evaluation was focused on the complementary behavior with these glycopeptides. A screening procedure was used based on previous work for the enantiomeric separation of 50 chiral compounds including amino acids, pesticides, stimulants, and a variety of pharmaceuticals. Fast and efficient chiral separations resulted by using superficially porous (core-shell) particle supports. Overall, the vancomycin Edman degradation product (EDP) resembled TeicoShell with high enantioselectivity for acidic compounds in the polar ionic mode. The simultaneous enantiomeric separation of 5 racemic profens using liquid chromatography-mass spectrometry with EDP was performed in approximately 3?minutes. Other highlights include simultaneous liquid chromatography separations of rac-amphetamine and rac-methamphetamine with VancoShell, rac-pseudoephedrine and rac-ephedrine with NicoShell, and rac-dichlorprop and rac-haloxyfop with TeicoShell.
Chiral Manganese Aminopyridine Complexes: the Versatile Catalysts of Chemo- and Stereoselective Oxidations with H2O2
Ottenbacher, Roman V.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
, p. 78 - 90 (2017/10/06)
In the last decade, manganese(II) complexes with N-donor tetradentate aminopyridine ligands emerged as efficient catalysts of enantioselective epoxidation of olefins and direct selective oxidation of C?H groups in complex organic molecules, with environmentally benign oxidant hydrogen peroxide. In this personal account, we summarize the progress of these catalysts with regard to ligands design, structure-reactivity correlations, evaluation of the substrate scope, as well as mechanistic studies, shedding light on the nature of active sites and the mechanisms of selective oxygenations. Several practically promising catalytic syntheses with the aid of Mn aminopyridine catalysts are exemplified.
Measurement of stable isotope ratios in methylamphetamine: A link to its precursor source
Salouros, Helen,Sutton, Gordon J.,Howes, Joanna,Hibbert, D. Brynn,Collins, Michael
, p. 9400 - 9408 (2013/10/21)
The illicit drug methylamphetamine is often prepared from the precursor ephedrine or pseudoephedrine, which in turn are obtained by three processes: extraction from the Ephedra plant ("natural"), via fermentation of sugars ("semi-synthetic"), and by a "fully synthetic" route from propiophenone. We report the first method to differentiate between the three industrial routes used to produce the precursors ephedrine and pseudoephedrine by measurement of stable isotope ratios of nitrogen (δ15N), hydrogen (δ2H), and carbon (δ13C). Analysis of 782 samples of seized methylamphetamine allowed classification into three groups using k-means clustering or the expectation-maximization algorithm applied to a Gaussian mixture model. By preparation of 30 samples of ephedrine by the "fully synthetic" industrial process and measuring their δ15N, δ2H, and δ13C values, we observed that 15N becomes significantly depleted compared to the methylamine starting material. Conversion of ten ephedrine samples to methylamphetamine showed that this depletion is maintained in the final drug product, of which the δ15N, δ13C, and δ2H values were distinct from those of ephedrine and methylamphetamine samples of a semi-synthetic (fermentation pathway) origin. Combining modeling analysis with the new experiments and published information on the values of δ2H gave a definitive assignment of the three model groups, and equations to obtain probabilities for the precursor origin of any new sample. A simple rule of thumb is also presented. Making an assignment using delta values is particularly useful when no other chemical profiling information is available.
Synthesis of 2-Arylethylamines by the Curtius Rearrangement
Schulze, Matthias
experimental part, p. 1461 - 1476 (2010/07/08)
2-Arylethylamine derivatives were synthesized using the Curtius reaction and with three different methods of preparing the acyl azide functional group. Carbamates derived from isocyanate were convenient protecting groups for alkylation of amines. Starting from benzaldehyde, amphetamine was prepared in three steps through an oxazolidin-2-one intermediate in 62% overall yield. Copyright Taylor & Francis Group, LLC.
Polymer-immobilized catalyst for asymmetric hydrogenation of racemic α-(N-benzoyl-N-methylamino)propiophenone
Chiwara, Vinia Ipai,Haraguchi, Naoki,Itsuno, Shinichi
body text, p. 1391 - 1393 (2009/07/04)
Asymmetric hydrogenation of α-(N-benzoyl-N-methylami-no)propiophenone through dynamic kinetic resolution was performed by using a polymer-immobilized chiral diamine-ruthenium-BINAP-t-BuOK system in order to yield syn-β-amidealcoholexclusivelywithnearlyperfectenantioselectivity.
Asymmetric hydrogenation of aromatic ketones catalyzed by the TolBINAP/DMAPEN-ruthenium(II) complex: A significant effect of N-substituents of chiral 1,2-diamine ligands on enantioselectivity
Ooka, Hirohito,Arai, Noriyoshi,Azuma, Keita,Kurono, Nobuhito,Ohkuma, Takeshi
supporting information; experimental part, p. 9084 - 9093 (2009/04/11)
(Chemical Equation Presented) Asymmetric hydrogenation of acetophenone in the presence of Ru(II) catalysts coordinated by TolBINAP and a series of chiral 1,2-diamines was studied. The sense and degree of enantioselectivity were highly dependent on the N-substituents of the diamine ligands. The N-substituent effect was discussed in detail. Among these catalysts, the (S)-TolBINAP/(R)- DMAPEN-Ru(II) complex showed the highest enantioselectivity. The mode of enantioface selection was interpreted by using transition state models based on the X-ray structure of the catalyst precursor. The chiral catalyst effected the hydrogenation of alkyl aryl ketones and arylglyoxal dialkyl acetals to afford the chiral alcohol in >99% ee in the best cases. Hydrogenation of racemic benzoin methyl ether with the chiral catalyst through dynamic kinetic resolution gave the anti-alcohol (syn:anti = 3:97) in 98% ee, while the reaction of α-amidopropiophenones resulted in the syn-alcohols (symanti = 96:4 to >99:1) in >98% ee.
General asymmetric hydrogenation of α-branched aromatic ketones catalyzed by TolBINAP/DMAPEN-ruthenium(II) complex
Arai, Noriyoshi,Ooka, Hirohito,Azuma, Keita,Yabuuchi, Toshio,Kurono, Nobuhito,Inoue, Tsutomu,Ohkuma, Takeshi
, p. 939 - 941 (2007/10/03)
(Chemical Equation Presented) A catalyst system consisting of RuCl 2[(S)-tolbinap][(R)-dmapen] and t-C4H9OK in 2-propanol effects asymmetric hydrogenation of arylglyoxal dialkylacetals to give the α-hydroxy acetals in up to 98% ee. Hydrogenation of racemic α-amidopropiophenones under dynamic kinetic resolution predominantly gives the syn alcohols in up to 99% ee and >98% de, while the reaction of racemic bezoin methyl ether gives the anti alcohols in excellent stereoselectivity.
Nonracemic α-allenyl carbinols from asymmetric propargylation with the 10-trimethylsilyl-9-borabicyclo[3.3.2]decanes
Hernandez, Eliud,Soderquist, John A.
, p. 5397 - 5400 (2007/10/03)
(Chemical Equation Presented) The asymmetric propargylboration of aldehydes at -78°C in 98% ee). The reagents 1 are easily prepared in both enantiomeric forms with a simple Grignard procedure and air-stable borinate complexes 2. The ozonolysis of 6 proceeds smoothly through an acylsilane intermediate to give a TMS ester, which is hydrolyzed to the α-hydroxy acid quantitatively with water.
Convenient access to glutamic acid side chain homologues compatible with solid phase peptide synthesis
Ryan, Shannon J.,Zhang, Yongda,Kennan, Alan J.
, p. 4765 - 4767 (2007/10/03)
(Chemical Equation Presented) Preparation of several side chain length variants of glutamic acid is achieved via olefin cross metathesis of allyl glycine derivatives. The products are suitably protected for direct use in Fmoc solid-phase peptide synthesis, as demonstrated by successful synthesis of test sequences.
Diastereoselective reduction of α-aminoketones: Synthesis of anti- and syn-β-aminoalcohols
Fraser, David S.,Park, Sheldon B.,Chong, J. Michael
, p. 87 - 101 (2007/10/03)
Reduction of N-t-BOC-protected-N-alkyl α-aminoketones with LiEt 3BH or Li(S-Bu)3BH furnishes protected syn-β-aminoalcohols with high selectivities. In contrast, removal of the BOC group followed by reduction of the aminoketone gives anti-β- aminoalcohols with variable selectivities. With aromatic ketones, selectivities are typically high while aliphatic ketones show mediocre to high selectivities depending on steric considerations.