Studies on the asymmetric synthesis using aryl-epoxides

Abstract

Epoxides are not only biologically significant compounds but also versatile intermediates because they could undergo stereospecific nucleophilic ring opening to yield bifunctional compounds. We focused on the stereoselective opening reaction of various aryl-epoxides mediated by Trialkylaluminium. We examined solvents, temperature and substituents as factors influencing the selectivity. We found the optimal condition for syn-addition in hexane under high temperature. Bulkiness of an alkyl substituent on an aryl-epoxide and extent of electro-donating power of an aryl group significantly controlled the reaction path. We also studied ylide chemistry, especially sulfur-ylide, to prepare miscellaneous epoxides. Racemic trans-epoxides were conveniently prepared by the corresponding sulfonium salt generated from tetrahydrothiophene. Moreover, Goodman``s symmetric chiral sulfide was also tested for the synthesis of chiral epoxides. On the basis of this progress, we have successfully developed a versatile synthetic route to the triketide 8-lactones which are valuable building blocks of many natural products. In a bid to extend its scope in application we designed the synthesis of a pentaketide via tetra-ene system as a key intermediate. Furthermore, construction of hexaketides utilizing our methodology is now underway.