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Tandem asymmetric double Michael addition/internal nucleophilic substitution of the novel chiral source, 5-(l-menthyloxy)-3-bromo-2(5H)-furanone with nucleophilic alcohol compounds has been investigated. The tandem asymmetric reaction can afford four new stereogenic centers with one reaction and give optically pure spiro-cyclopropane derivatives 5a--5d which are difficult to obtain by routine methods. The synthetic method for 5a--5d was studied in detail and the new compounds were identified on the basis of their analytical data and spectroscopic data, such as [α]~(20),IR,~1H NMR,~(13)C NMR, MS and elementary analysis. The absolute configuration of the sprio [5-l-menthyloxy-3-bromo butyrolactocyclopropane-3″, 3′(4′-methyloxy-5′-menthyloxybutyrolactone)] (5a) was established by X-ray crystallography. The work can provide important synthetic strategy in synthesis of some new optically active spiro-cyclopropane analogues and some biologically active molecules with complex structure.
Tandem asymmetric double Michael addition / internal nucleophilic substitution of the novel chiral source, 5- (l-menthyloxy) -3-bromo-2 (5H) -furanone with nucleophilic alcohol compounds has been investigated. centers with one reaction and give optically pure spiro-cyclopropane derivatives 5a-5d which are difficult to obtain by routine methods. The synthetic method for 5a-5d was studied in detail and the new compounds were identified on the basis of their analytical data 1H NMR, ~ (13) C NMR, MS and elementary analysis. The absolute configuration of the sprio [5-l-menthyloxy-3-bromo butyrolactocyclopropane- 3 ", 3 ’(4’-methyloxy-5’-menthyloxybutyrolactone)] (5a) was established by X-ray crystallography. The work can provide important synthetic strategy in synthesis of some new optically active spiro-cyclopropane analogues and some biologically active molecules with complex structu re.