Stereoselective Synthesis of Highly Substituted Bicyclic γ-Lactones Using Homoaldol Addition of 1-(1-Cycloalkenyl)methyl Carbamates

Abstract

Stereoselective addition of aldehydes 4 to metallated 1-(1-cycloalkenyl)methyl N,N-diisopropylcarbamates 1 gave cyclic homoaldol adducts 6. By applying the (-)-sparteine method, enantiomerically enriched products were obtained. These were oxidatively cyclized to diastereomerically pure γ-lactones 8 via the γ-lactol ethers 7. After deprotonation of γ-lactones 8 with lithium hexamethyldisilazide, a further substitution was achieved. By trapping the lactone enolates 11 with β-naphthylmethyl bromide, single dia­stereomers of γ-lactones 12 were produced.

asymmetric synthesis - 1-alkenyl carbamates - homoaldol addition - (-)-sparteine - bicyclic lactones

References

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<A NAME="RT03604SS-12">12</A> Data sets were collected with an Enraf-Nonius CAD4 diffractometer. Programs used: data collection EXPRESS (Nonius B.V., 1994), data reduction MolEN (K. Fair, Enraf-Nonius B.V., 1990), structure solution SHELXS-97 ( Sheldrick GM. Acta Cryst.  1990,  A46:  467 ), structure refinement SHELXL-97 (G. M. Sheldrick, Universität Göttingen, 1997), graphics MOPICT 3.2 (M. Brüggemann, Universität Münster, 2001). Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication CCDC 182787 and 182786. Copies of the data can be obtained free of charge on application to The Director, CCDC, 12 Union Road, CambridgeCB2 1EZ, UK [fax: int. code [phone], e-mail: [e-mail]]

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Prasad, K. R.; Özlügedik, M.; Wibbeling, B.; Fröhlich, R.; Hoppe, D., manuscript in preparation.

<A NAME="RT03604SS-15">15</A>

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