N-Methyloxazolinium salts: diastereomer ratios by proton NMR (original) (raw)
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Enol oxalacetic acid exists in the Z form in the crystalline state and in solution
The Journal of Organic Chemistry, 1992
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Innovative Publisher, 2023
The stratagem for literature searching in organic and inorganic synthesis increasingly becomes easier with the computer database. However, the dilemma has now become how to select one procedure instead of other. For neophyte, this is a difficult task, deciding the reaction conditions to be carried out to have the best chance of success. This practical procedure collection intended to serve lab-mate by sharing author’s own experience through most commonly used experimental procedures from established groups, reviewed journals and/or patents. Under the title of each experimental procedure, brief commentaries are often offered which summarize the authors’ personal experience. For the final products, detailed spectral data are not given because they simply take up too much space. We had a good time putting together these experimental procedures. We have even been using the manuscript ourselves quite often. Hopefully, you will find it as useful. We welcome your critique.
International Journal of Advanced Research
Scheme-1 Prop-2-yn-1-yl 3-((tert-butoxycarbonyl)amino)-2,2-dimethylpropanoate Step-1 Dicyclohexylcarbodiimide (1.1 eq.) and triethylamine (2 eq.) were added to a stirred solution of compd-1 (1 eq.) and Compd-2 (1 eq.) in 1 : 1 ratio of Dichloromethane (DCM) : Dimethylformamide (10 mL/ 1 g) at 0°C. The reaction mixture was stirred at room temperature for 16 hours. After completion of reaction (checked by TLC), solid waste was filtered. The resultant filtrate was diluted with DCM, followed by washing with water, dried over anhydrous sodium sulphate (Na2SO4) and concentrated. The obtain crude material was purified by Silica gel (100-200 mesh) column chromatography using (2:8) ethyl acetate in hexane.
Conversion of L-tyrosine to L-phenylalanine. Preparation of L-[3',5'-13C2]phenylalanine
The Journal of Organic Chemistry, 1980
07% probably not as good as could be realized by use of chromatographic or chemical (picrate formation and regeneration, for example) methods of separation. Experimental Section 1,5-Dimethylnaphthalene. The alcohol l-(2-methylphenyl)-1-pentanol (1) was prepared in the usual way from freshly distilled 2-methylbenzaldehyde (53.6 g, 0.45 mol) and an ethereal solution of n-butylmagnesium bromide prepared from 14.7 g (0.60 mol) of magnesium arid 95.6 g (0.698 mol) of 1-bromobutane. The yield of alcohol distilling a t 119-132 "C (1.8 torr) was 60.3 g (75.5%) [lit! bp 84 "C (0.6 torr)]. The alcohol 1 (56.3 g, 0.32 mol) was heated in a simple distillation apparatus with 3 g of phosphorus pentoxide until the distillation of water ceased. Some organic material that. had distilled with the water was returned to the flask. The flask was fitted with an upright air-cooled reflux condenser, 2 g of fresh Pz05 was added, and the mixture was refluxed 2 h. It was then distilled under reduced pressure. A middle fraction, 27.2 g, distilling at 95-210 "C (23 torr), was redistilled and yielded 23.8 g (46.4% as C12H16) distilling a t 119-126 "C (21 torr). Analysis by NMR spectroscopy and GLC' indicated a mixture containing 69.8% 1,5-dimethyl-1,2,3,4tetrahydronaphthalene. The mixture (23.0 g) was heated with 1 g of 10% palladium on charcoal catalyst 4 h. The catalyst was removed by filtration with suction while the mixture was still hot. 1,5-Dimethylnaphthalene crystallized in the filtrate and was recrystallized from ethanol: yield 9.67 g (43.1%); mp 75 "C (lit.2a mp 77-78 "C). cr-Butyl-l-naphthalenemethanols (2). A Grignard reagent was prepared in ether from 24.32 g (1 mol) of Mg and 217.8 g (1.05 mol) of 1-bromonaphthalene. To this was added an ethereal solution of 77.6 g (0.90 mol) of freshly distilled pentanal [bp 25-30 "C (24 torr)]. The semisolid reaction mixture was refluxed with stirring for 0.5 h. After workup in the usual way, an attempt was made to distill the product under reduced pressure. After removal of a small forerun distilling to 85 "C (5 torr), the distillate began to solidify in the side arm of the Claisen flask being used, and the attempt at distillation was abandoned. The residue in the flask solidified upon cooling and was used without further purification: yield 195.3 g; mp 56-62 "C (lit.6 mp 65-66 "C). This crude product probably contained naphthalene and l-bromonaphthalene as impurities.
Supporting Information Part I. Chemical Synthesis and Characterization General Procedures
All reagents were purchased from Sigma-Aldrich (St Louis, MO, USA) or Macrocyclics (Dallas, TX, USA) unless stated otherwise. Solvents were freshly distilled on appropriate driers and reactions run under an inert Argon atmosphere (CH 2 Cl 2 was distilled over P 2 O 5 , THF was distilled over sodium). All compounds apart from those containing Gd were fully characterized by 1 H (400 Hz) NMR, 13 C (400 Hz) (Bruker AMX-400 spectrometer) and the final products with Gd were characterized by mass spectrometry (EIMS and HRMS). Chemical shifts are expressed in δ ppm. All photophysical experiments were carried out using spectroscopic-grade solvents. Column chromatography was performed either over Silica Gel 60 (70-230 mesh) or neutral Alumina (Brockmann grade III, 50 mesh). UV-visible spectra were recorded on Varian Cary 50 Bio UV-visible spectrophotometer using CH 2 Cl 2 as solvent unless otherwise specified. Fluorescence spectra were recorded on a Varian Cary Eclipse fluorescence spectrophotometer with an excitation wavelength in the "Soret" band region between 410 and 425 nm.
Methods for syntheses of N-methyl-DL-aspartic acid derivatives
Amino Acids, 2007
A novel practical method for the synthesis of N-methyl-DLaspartic acid 1 (NMA) and new syntheses for N-methyl-aspartic acid derivatives are described. NMA 1, the natural amino acid was synthesized by Michael addition of methylamine to dimethyl fumarate 5. Fumaric or maleic acid mono-ester and-amide were regioselectively transformed into beta-substituted aspartic acid derivatives. In the cases of maleamic 11a or fumaramic esters 11b, the a-amide derivative 13 was formed, but hydrolysis of the product provided N-methyl-DL-asparagine 9 via base catalyzed ring closure to DL-a-methylamino-succinimide 4, followed by selective ring opening. Efficient methods were developed for the preparation of NMA-a-amide 13 from unprotected NMA via sulphinamide anhydride 15 and aspartic anhydride 3 intermediate products. NMA diamide 16 was prepared from NMA dimethyl ester 6 and methylamino-succinimide 4 by ammonolysis. Temperature-dependent side reactions of methylamino-succinimide 4 led to diazocinone 18, resulted from self-condensation of methylamino-succinimide via nucleophyl ring opening and the subsequent ring-transformation.