• YAKHAK HOEJI
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• v.39 no.2
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• pp.205-209
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• 1995

Methylene protons of benzyl and ethyl ester in ethyl 1-benzyl-2, 3-dioxo-cyclopenta[b]-pyrrole-3a-carboxylate (A) exhibited opposite$^{1}$H-NMR spectral patterns mutually between magnetic equivalence and nonequivalence depending on concentration and temperature. The diastereotopic spectral data of compound A were reported with brief interpretation.

• Analytical Science and Technology
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• v.18 no.1
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• pp.85-88
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• 2005

Antiphase character of cross peaks in long-range COSY is modulated by changing the fixed delay time and used to assign diastereotopic methylene protons on rigid systems which could produce unpredictable NOE phenomena because of complicate coupling spins.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1145-1148
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• 1999

1H NMR spectra of methyl-, ethyl-, propyl-, isopropyl-, butyl-, N-methylethyl-, N-methylpropyl-, and N-methylisopropylamine coordinated to the paramagnetic 11-tungstocobalto(II)silicate anion (SiW11Co) in dimethylsulfoxide-d6 or dimethylformamide-d7 are reported. For these complexes the ligand exchange is slow on the NMR time scale and pure 1H NMR signals have been observed at room temperature. No complex is detected in D2O. From the pseudocontact shifts of the CH2 and CH3 groups in ethylamine the energy of the gauche conformers with respect to the anti conformer is estimated. Two diastereotopic protons in the CH2 group of N-methylethylamine have quite different chemical shifts especially at low temperatures (e.g. 48.5 vs. 19.4 ppm at -10℃). This may be attributed mainly to the different positions of the two protons in the most stable (gauche) conformer.

• YAKHAK HOEJI
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• v.38 no.5
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• pp.544-554
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• 1994

Pyrrolidine-2,3-dione derivative A was synthesized from oxalylation of chiral enamine Ba. The stereostructure of its major diastereomer $(A_{maj})$ was determined as octahydro-2,3-dioxo-6aS-hyd roxy-1-(1S-methoxycarbonyl-2-phenylethyl)-cyclopenta[b]pyrrole-3aR-carboxylic acid ethyl ester Aa by means of NMR spectrum. This result implied that the asymmetric carbon-carbon bond forming reaction occurred preferentially at the ${\beta}-face$ of Ba.