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DOI: 10.1055/s-2004-831170
Stereoselective Synthesis of Highly Substituted Bicyclic γ-Lactones Using Homoaldol Addition of 1-(1-Cycloalkenyl)methyl Carbamates
Publication History
Publication Date:
19 August 2004 (online)
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.
Key words
asymmetric synthesis - 1-alkenyl carbamates - homoaldol addition - (-)-sparteine - bicyclic lactones
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References
Responsible for X-Ray crystal structure data.
7In related cases, we recently observed an oxidative dimer of 1. We suspect that a one-electron transfer from titanium to the allylic anion is the cause. The use of ClTi(NEt2)3 as exchange reagent is recommended.3d
14Prasad, K. R.; Özlügedik, M.; Wibbeling, B.; Fröhlich, R.; Hoppe, D., manuscript in preparation.
15Determined via the lactone derivative.