2368
N. Kise, N. Ueda / Tetrahedron Letters 42 (2001) 2365–2368
basic alumina (hexane/ethyl acetate). Recrystallization
of the mixture from hexane/ethyl acetate (10/1) gave
pure meso-2a in 35% yield.
J. Org. Chem. 1999, 64, 7665.
5. Shono, T.; Kise, N.; Shirakawa, E.; Matsumoto, H.;
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11. The diastereomeric ratios of 2 were determined by their
1H NMR spectra. The chemical shifts (l) of methyn
protons adjacent to the nitrogen atom in 2 were as
follows: dl-2a 4.09; meso-2a 4.01; dl-2b 4.07; meso-2b
3.95; dl-2c 4.01; meso-2c 3.93; dl-2d 3.99; meso-2d 3.97;
dl-2e 4.14; meso-2e 4.09; dl-2f 4.01; meso-2f 3.86; dl-2g
4.28; meso-2g 4.22; dl-2h 4.03; meso-2h 3.96; dl-2i 4.67;
meso-2i 4.71; dl-2j 5.11; meso-2j 5.23; dl-2k 4.42; meso-2k
4.29.
3. (a) Annunziata, R.; Benaglia, M.; Cinquini, M.; Cozzi,
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.