Glycal epoxides, openings with

Evans developed a new method for the synthesis of [(-C-allylglycosides, based on BusSnOTf-mediated ring-opening of glycal epoxides with allylstannanes as nucleophiles [81a], This methodology has been efficiently used in the (3-stereoselective introduction of the side chain (C44-C51) of spongistatin 2 (Scheme 8.43) [81b,c]. 

The opening of epoxides with zinc reagents is a difficult reaction. However, activated epoxides such as the glycal epoxides 225 react with diorganozincs in the presence... 

Experimental. Opening of glycal epoxide with ethylthiol [63] A suspension of polymer-bound glycal 35 (1.0 g) in dichloromethane (20 mL) was treated with dimethyldioxirane as described previously to give epoxide 36. This resin was suspended in a mixture of dichloromethane (10 mL) and ethanethiol (10 mL), cooled to —78°C, and treated with trifluoroacetic an-... 

There are limited data on 1,2-epoxy of glycal epoxide ring opening reaction with C-nucleophiles other than organocuprate, e.g., Grignard reagents [217, 218], organolithium compounds [217-219], aUylstannane [217], and sodio di-tert-butyl malonate [219, 220]. 

In 2003, the first report of glycal oxidation with MTO as the catalyst and UHP as the oxidant was published by Goti and coworkers. In methanol as the solvent, triacetyl- and tribenzylglucal are epoxidized, followed by ring opening of the... 

Glycal assembly method (Section 25.9) a method of polysaccharide synthesis in which a glycal is converted into its epoxide, which is then opened by reaction with an alcohol. 

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