1704
S. Seyhan et al. / Tetrahedron: Asymmetry 17 (2006) 1700–1704
4.2.3. (S)-2-Isobutyl-N-benzyl-4,7,10,13-tetraoxa-8,9-benzo-
1-azacyclopentadec-8-ene 4. To a suspension of NaH
(2.15 g, 0.0715 mol, % 80 in mineral oil) in 100 mL dry
THF at 0 ꢁC was added a solution of diol 3 (4 g,
0.021 mol) in 250 mL of THF. The reaction mixture was
refluxed for 2 h. After cooling to 0 ꢁC, a solution of 1,2-
bis-(2-p-tolylsulfonyl ethoxy) benzene (10.62 g, 0.021 mol)
in 250 mL of THF was slowly added to the reaction mix-
ture. The suspension was refluxed for 50 h. The solvent
was evaporated and 100 mL of water was added to the res-
idue. The mixture was extracted with CH2CI2 (3 · 150).
The combined organic layers were washed with 100 mL
water again, dried on anhydrous Na2SO4, and the solvent
was evaporated. The crude product was purified by flash
column chromatography on silica gel (eluent: triethyl-
4.2.6. Column experiments. The chiral crown ether (0.1 g)
on Amberlite XAD-16 and 0.1 g of the chiral crown ether
on derivatized silica gel were firstly wetted with 5 mL meth-
anol and stirred for 10 min, and then 5 mL of doubly
deionized water was added and stirred for 10 min again.
Lastly, the mixture was transferred to the polyethylene col-
umn and 25 mL of methanol–water (10:90) was passed
through the column. A sample solution containing amino
acid (phenylalanine or phenylglycine or tryptophan as their
potassium or sodium salts) was taken and the pH was ad-
justed to ꢂ10.5 and passed through the above column.
Then, the amino acids were stripped from the column with
doubly deionized water and determined spectrophotomet-
rically at 253 nm (for phenylalanine and phenylglycine)
and 280 nm (for tryptophan). All runs were carried out at
ambient temperature (23–25 ꢁC).
amine–ethyl acetate–petroleum ether 60–80 = 3:17:80) to
20
give 4 g (61%); ½aꢁD ¼ ꢀ11:6 (c 1.4, CHCl3), IR: m 3070,
3031, 2940, 2877, 1592, 1503, 1458, 1362, 1259, 1227,
1
1131, 1053, 938, 783, 739, 707 cmꢀ1; H NMR (CDCI3)
References
d 0.88–0.95 (m, 6H), 1.21–1.81 (m, 3H), 2.86–3.13 (m,
3H), 3.62–3.88 (m, 10H), 4.12–4.20 (m, 4H), 6.90–6.98
(m, 4H), 7.22–7.40 (m, 5H); 13C NMR (CDCI3) d 22.99,
23.71, 25.39, 38.47, 50.63, 55.99, 58.34, 69.32, 69.88,
69.97, 70.95, 71.93, 73.80, 113.85, 121.63, 126.99, 128.48,
129.00, 141.71, 149.43; Anal. Calcd for C25H35NO4: C,
72.64; H, 8.47; N, 3.30. Found: C, 72.40; H, 8.10; N, 3.10.
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4.2.4. Preparation of monoamine modified silica gel. Ten
grams of dry silica gel (70–230 mesh) was mixed with
50 mL dry toluene and 12 mL of 3-aminopropylmethoxy-
silane in a round-bottomed flask and refluxed overnight.
The reaction mixture was left to cool, filtered off, and
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dried at 60 ꢁC for 6 h.
4.2.5. Impregnation process. Amounts of 0.1 g portion of
dry Amberlite XAD-16 and the aminopropyl modified sil-
ica gel were contacted with 25.0 mL of chiral crown ether
solution and stirred for 24 h. The impregnated resin and
impregnated aminopropyl modified silica gel were sepa-
rated by filtration through a sintered glass funnel and
were washed with water to remove the solvent. The resin
and the silica gel were used as air-dried products. The
CSP-1 and CSP-2 contents in the impregnated solution
were determined gravimetrically, by weighing the dry li-
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of solution. The amounts of impregnated Amberlite
XAD-16 (CSP-1, 72%) and aminopropyl modified silica
gel (CSP-2 63%) were calculated from the material
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