3314
P. Merino et al. / Tetrahedron Letters 47 (2006) 3311–3314
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1957–1965.
diastereomeric hydroxylamines 2a and 3a into enantio-
meric protected derivatives of allylglycine (Scheme 3).
Deoxygenation of the hydroxyamino function, N-pro-
tection and further transformation of the dioxolane ring
into a carboxyl group,19 afforded 5 and ent-5 in good
overall yields.
6. (a) Lombardo, M.; Spada, S.; Trombini, C. Eur. J. Org.
Chem. 1998, 2361–2364; (b) Gianotti, M.; Lombardo, M.;
Trombini, C. Tetrahedron Lett. 1998, 39, 1643–1646; (c)
Mancini, F.; Piazza, M. G.; Trombini, C. J. Org. Chem.
1991, 56, 4246–4252.
7. (a) Dhavale, D. D.; Gentilucci, L.; Piazza, M. G.;
Trombini, C. Liebigs Ann. Chem. 1992, 1289–1295; (b)
Dhavale, D. D.; Jachak, S. M.; Karche, N. P.; Trombini,
C. Tetrahedron 2004, 60, 3009–3016.
8. Fiumana, A.; Lombardo, M.; Trombini, C. J. Org. Chem.
1997, 62, 5623–5626.
9. (a) Merino, P. C.R. Acad. Sci., Ser. IIc: Chim. 2005, 8,
775–778; (b) Merino, P.; Franco, S.; Merchan, F. L.;
Tejero, T. Synlett 2000, 442–454.
10. Dondoni, A.; Franco, S.; Junquera, F.; Merchan, F.;
Merino, P.; Tejero, T. Synth. Commun. 1994, 24, 2537–
2550.
11. Typical procedure: To a solution of nitrone (1.0 equiv) in
the indicated solvent and temperature (see Table 1),
1.0 equiv of Lewis acid was added. After 5 min, 2.0 equiv
of the allylic metal was added and the reaction mixture
was stirred until no more nitrone (TLC) was observed. A
saturated aq solution of NH4Cl was added and the
resulting mixture was diluted with diethyl ether. The
organic layer was separated, dried (MgSO4) and evapo-
rated to furnish the crude product, which was purified by
radial chromatography.
In this letter we have described the successful applica-
tion of Lewis acids to control the diastereofacial selectiv-
ity in allylation reactions of chiral non-racemic a-alkoxy
nitrones. We have also demonstrated the utility of the
methodology by preparing N-Boc-L-allylglycine and its
enantiomer. The effect of the Lewis acid in the stereo-
chemical course of the allylation reaction is a matter
of interest, and further studies are in progress.
Acknowledgements
We thank the Ministerio de Educacion y Ciencia (MEC,
Project CTQ2004-0421), and the Regional Government
of Aragon (DGA) for financial support. I.D. and V.M.
thanks DGA and MEC, respectively, for pre-doctoral
grants. Hortensia Rico, Michael Roessler and Sasha
Schaeffer are acknowledged for exploratory work.
12. Seyferth, D.; Weiner, M. A. Org. Synth. 1973, 5, 452
(freely available on the Internet).
References and notes
13. (a) Merino, P.; Franco, S.; Merchan, F. L.; Tejero, T. J.
Org. Chem. 1998, 63, 5627–5630; (b) Merino, P.; Lanaspa,
A.; Merchan, F. L.; Tejero, T. Tetrahedron: Asymmetry
1998, 9, 629–646. See also Ref. 9 and references cited
therein.
14. Merino, P.; Tejero, T. Tetrahedron 2001, 57, 8125–8128.
15. Laskar, D. D.; Prajapati, D.; Sandhu, J. S. Tetrahedron
Lett. 2001, 42, 7883–7886.
16. Kumar, H. M. S.; Anjaneyulu, S.; Reddy, E. J.; Yadav,
J. S. Tetrahedron Lett. 2000, 41, 9311–9314.
17. Merino, P.; Franco, S.; Gascon, J. M.; Merchan, F. L.;
Tejero, T. Tetrahedron: Asymmetry 1999, 10, 1861–
1865.
1. Ding, H.; Friestad, G. K. Synthesis 2005, 2815–2829.
2. Merino, P.; Tejero, T.; Delso, J. I.; Mannucci, V. Curr.
Org. Synth. 2005, 2, 479–498.
3. For recent and representative examples see: (a) Shimizu,
M.; Kimura, M.; Watanabe, T.; Tamaru, Y. Org. Lett.
2005, 7, 637–640; (b) Smitha, G.; Miriyala, B.; William-
son, J. S. Synlett 2005, 839–841; (c) Vilaivan, T.; Wino-
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Org. Chem. 2005, 70, 3464–3471; (d) Foubelo, F.; Yus, M.
Tetrahedron: Asymmetry 2004, 15, 3823–3825; (e) Lee,
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4. (a) Fernandes, R. A.; Yamamoto, Y. J. Org. Chem. 2004,
69, 3562–3564, and references cited therein; For a review
see: (b) Yamamoto, Y.; Asao, N. Chem. Rev. 1993, 93,
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18. All compounds gave satisfactory elemental analysis and
their structure was identified by NMR spectroscopy.
19. Merino, P.; Castillo, E.; Franco, S.; Merchan, F. L.;
Tejero, T. J. Org. Chem. 1998, 63, 2371–2374.