Highly optically active 4-substituted-2(5H)-furanones 6a--6j were obtained in good yields with de 398% by the tandem Michael additiodelimination reaction of chiral 3-bromo-2(5H)-furanone (4a), which was conveniently prepared starting from 2-furaldehyde under mild conditions. The products were identified on the basis of their satisfactory elemental analysis and spectroscopic data of IR, W, 'H NMR, "C NMR and mass spectra. The stereochemistry and absolute configuration of this type of compounds were established by the X-ray crystallographic study. The reaction provided a short and efficient synthesis of the interesting highly optically active 4-substituted-2(5H)-furanones containing an active pyrimidine and a purine base group. Keywords action, pyrimidine or purine base group, X-ray crystallography optically active 4-substituted-2(5H)-furanone, tandem asymmetric Michael additiodelimination reButenolide derivatives are a group of important compounds containing unique carbon skeleton of 2(5H)-furanone which is widely present in many natural products.'-3 They exhibit a variety of biological properties and have been considered as potential anti-tumor agents, fungicides, bactericides, insecticides, antibiotics, antiinflammatories, allergy inhibitors, antipsoriasis agents, cyclooxygenase inhibitors, phospholipase A2 inhibitors, some microbial degradable products and so Thus, much attention has been paid to the new asymmetric methods for synthesis of these interesting c o r n p o~n d s .~~'~ The well-known chiral 5-(R)-menthyloxy-2(5H)-furanone behaves as a Micheal acceptor towards carbon, oxygen, sulphur and nitrogen nucleophiles to afford chiral 4-(R)-menthyloxy-3-substituted butyrolactone via a simple MichealThe 5-(R)-menthyloxy-3,4-dihalo(chloro, bromo)-2(5H)-furanone reacts with corresponding nucleophiles to give chiral5-(R)-menthyloxy-4-substituted-3-halo-2(5H)-furanone compounds via a tandem asymmetric Michael additiodelimination reRecently, we successfully synthesized the novel chiral synthon, 5-(R)-( -)-menthyloxy-3-bromo-2(5H)-furanone (4a) in good yield with de 3 98% through a valuable synthetic route and applied the tandem double Michael additiodinternal substitution of chiron 4a to various nucleophiles to obtain the novel functionalized spiro-cyclopropanes containing multiple stereogenic centers.l7-I9 The reaction of the heterocyclic amines 5a-Sc with chiral synthon 4a in a molar ratio of 1 2 underwent the expected reaction to form the spiro-cyclopropane products containing heterocyclic amino groups in 25%-30% yields. The stereochemistry and absolute configuration of the chiral spirocyclopropanes were characterized by spectroscopic data as well as X-ray crystallography." The regioselective and stereoselective transformation of the auxiliary group in the obtained spiro-cyclopropane derivatives were also investigated.2a22 Results and discussionOn the basis of previous work, we have accomplished the tandem Michael additiodelimination reaction of chiral synthon 4a with different nucleophiles, such as the heterocy...
Scheme 1. Synthetic route to racemic diethyl a-hydroxy-substitutedphosphonate 3 + 3'. R: a= ( ) -; b= 0-; c= 0-; d= Cl-Q-
A new chemical hamsfomtion for the aMstruction of diversely functionalized cydopmpane-phosphorw derivativg utilizing chiron 4 and racemic diethyl a-hydmxyibeqlphsphonate 8s the key prerursors is d e s c r i i . 'Ibe diasterromeric pure phosphorwcwtaining derivatives Sa, S a , 5b and 5'b were obtained rrspectively, in good yields with d . e . >98% via asymmetric taodem double Michael additiodinternal nucleophilic substitution of the corresponding compolmds and further thmugh the separation of the diastereomeric mixhup by column chromatography. The diversely functionalized phosphorus derivatives are identified on the basis of their elemental analysis and spectroscopic data, such 8s IR, 'H NMR, "C NMR and MS. The absolute configuration of the interesting cyclopmpanephosphorus compound 5a was established by X-ray nystallography. Thus, these results provide a valuable strategy for synthesizing some biologically active molecules.
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