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16. N-(2-Hydroxyethyl)carboxamides
4 were prepared in
excellent yields from the corresponding acid chlorides and
2-hydroxethylamines (1.5 equiv.) in the presence of Et3N
(1.5 equiv.) in CH2Cl2 at room temperature.
17. The diastereomeric isomer of 5 afforded (R)-6 in 95%
yield by the reaction with NaOMe in DMC within 1 h at
room temperature.
18. Enantiomeric excess of 6 (>99% ee) was determined by
HPLC with Daicel CHIRALCEL OD column (1% IPA
in hexane).
8. Evans, D. A.; Chapman, K. T.; Bisaha, J. J. Am. Chem.
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9. Selective transesterification of N-acyloxazolidinones was
reported using lanthanum(III) catalysts recently. See: (a)
Fukuzawa, S.; Hongo, Y. Tetrahedron Lett. 1998, 39,
3521–3524; (b) Orita, A.; Nagano, Y.; Hirano, J.; Otera,
J. Synlett 2001, 637–639.
10. Kanomata, N.; Ochiai, Y. Tetrahedron Lett. 2001, 42,
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11. Kanomata, N.; Oikawa, J. Tetrahedron Lett. 2003, 18,
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Engl. 1997, 36, 1207–1211; (b) Kanomata, N.; Nakata, T.
J. Am. Chem. Soc. 2000, 122, 4563–4568.
13. N-Acyl-2-oxazolidinones 1 were prepared from the corres-
ponding acid chlorides and deprotonated (S)-4-isopropyl-
2-oxazolidinone 3 based on the known procedure. See:
Gage, J. R.; Evans, D. A. Org. Synth. Coll. VIII 1993,
339–343.
14. Stereochemistry of 1e,f was assigned as shown in Table 1
by comparison with 1H NMR spectral data of 1f reported
in literature. See: Miyata, O.; Shinada, T.; Ninomiya, I.;
Naito, T. Tetrahedron 1997, 53, 2421–2438.
15. To determine absolute configuration of (S)-(+)-2f and
(R)-(−)-2h, the latter ester was hydrolyzed to (R)-(−)-2-
19. Experimental procedures: A solution of bridged nicotin-
amide (S,3%S)-7x (357 mg, 1.03 mmol), sodium methoxide
(278 mg, 5.15 mmol), and dimethyl carbonate (0.42 ml,
5.15 mmol) in CH2Cl2 (5 ml) was stirred at room temper-
ature for 18 h. After the reaction was complete, water (5
ml) was added and the organic layer was separated. The
aqueous layer was acidified to ca. pH 7 with hydrochloric
acid and was extracted with CH2Cl2 (3×). The combined
organic layer was dried over MgSO4, filtered, and con-
centrated in vacuo. The mixture was chromatographed
on silica gel by ether–hexane (1/2) to give (S)-6 (278 mg,
98%) and by ether to give 4-isopropyl-2-oxazolidinone (3)
(128 mg, 96%).
20. For the synthetic application of planar-chiral
cyclophanes, see: (a) Dahmen, S.; Bra¨se, S. Org. Lett.
2001, 3, 4119–4122; Dahmen, S.; Bra¨se, S. J. Am. Chem.
Soc. 2002, 124, 5940–5941; Hermanns, N.; Dahmen, S.;
Bolm, C.; Bra¨se, S. Angew. Chem., Int. Ed. 2002, 41,
3692–3694; (b) Cipiciani, A.; Fringuelli, F.; Piermatti, O.;
Pizzo, F.; Ruzziconi, R. J. Org. Chem. 2002, 67, 2665–
2670.