Epoxides ring-opening reactions have been

Complexes of other metals such as gallium, indium, lead, and antimony have also been used as Lewis acids. Catalytic enantioselective meso-epoxide ring-opening reactions using a chiral gallium(III) catalyst (Ga-Li-linked-BINOL) have been reported (Scheme 84).348 The chemical yields are much improved by linking two BINOL units. 

Epoxide rings in sugars have been opened by the action of halogen acids. Both possible products of ring scission were observed in the reaction of methyl 2,3-anhydro-4,6-O-benzylidene-a-D-alloside 8 with hydrobromic... 

Two classes of structures containing azido- and aziridino-hydroxyl-(3-lactam (I and II, respectively, Fig. 21) have been prepared by means of a stereo- and regioselective epoxide ring opening reaction [296],... 

Epoxide ring-opening reactions with various nitrogen heterocycles (indoles, pyrroles, pyrazoles) have been efficiently promoted under mild conditions with high pressure or silica gel-catalysed conditions. 

Esters of (2,2-difluoro-3,4-dihydroxybutyl)phosphonic acid have been obtained through an epoxide ring-opening reaction ", and such a procedure has also been successfully applied to the preparation of mono-, di- and tri-hydroxy acids depending on the nature of the oxirane substituents (reaction 13)(X , = CH2Ph or / -toluenesulphonyl, or... 

Some additional examples are given in Scheme 8.6. The electrophiles that have been used successfully include iodine (Entries 2 and 3) and cyanogen chloride (Entry 4). The adducts can undergo conjugate addition (Entry 5), alkylation (Entry 6), or epoxide ring opening (Entries 7 and 8). The latter reaction is an early step of a synthesis of epothilone B. 

The asymmetric oxidation of organic compounds, especially the epoxidation, dihydroxylation, aminohydroxylation, aziridination, and related reactions have been extensively studied and found widespread applications in the asymmetric synthesis of many important compounds. Like many other asymmetric reactions discussed in other chapters of this book, oxidation systems have been developed and extended steadily over the years in order to attain high stereoselectivity. This chapter on oxidation is organized into several key topics. The first section covers the formation of epoxides from allylic alcohols or their derivatives and the corresponding ring-opening reactions of the thus formed 2,3-epoxy alcohols. The second part deals with dihydroxylation reactions, which can provide diols from olefins. The third section delineates the recently discovered aminohydroxylation of olefins. The fourth topic involves the oxidation of unfunc-tionalized olefins. The chapter ends with a discussion of the oxidation of eno-lates and asymmetric aziridination reactions. 

Several methods have been developed for the synthesis of the taxol side chain. We present here the asymmetric construction of this molecule via asymmetric epoxidation and asymmetric ring-opening reactions, asymmetric dihydroxylation and asymmetric aminohydroxylation reaction, asymmetric aldol reactions, as well as asymmetric Mannich reactions. 

Using the catalytic system described above, the enantioselective opening of meso epoxides could also be pursued. Although many excellent examples of ring-opening of meso epoxides by Sn2 reactions have recently been reported, the reaction planned here is conceptually different [40]. In the SN2 reaction, the path of the incoming nucleophile has to be controlled. In the titanocene-catalyzed reaction, the intermediate radical has to be formed selectively. If an intermediate similar to that invoked in the Bartmann ring-open-... 

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