Synthetic applications of glycal-derived allyl epoxides and aziridines. Synthesis, regio- and stereoselectivity of corresponding carba analogous epoxides in nucleophilic addition reactions.

This thesis deals with the reactivity and synthetic use of glycal-derived allyl epoxides, allyl aziridines and of the new corresponding carba analogs. In particular, the complete substrate-dependent O-glycosilation process previously found in O-glycosilation of alcohols by epoxide 2.1β and N-nosyl aziridine 2.3α was adapted in a reiterative version for the construction of 2,3-unsaturated-1,6-oligosaccharides, also bearing a free amino group at C(4) carbon. Subsequent completely stereoselective dihydroxylation afforded corresponding fully substituted 1,6-oligosaccharides. The reaction of N-mesyl substituted allyl aziridines 2.2α,β derived from D-allal and D-galactal with N-, S- and C-nucleophiles indicated that the occurrence of an oxirane oxygen-nucleophile coordination can modify the commonly observed anti-1,2-regio- and stereoselectivity into syn-1,4-regio- and stereoselectivity with the obtainment of corresponding syn-1,4-addition products. Epoxides 6.14α and 6.14β, the carba analogs of glycal-derived epoxides 2.1α and 2.1β were synthesized and their regio- and stereochemical behaviour examined, particularly with O-nucleophiles. Whereas epoxide 6.14β turned out to give highly or completely anti-1,2-regio- and stereoselective addition reactions, epoxide 6.14α showed a high 1,4-regioselectivity which makes this epoxide an effective candidate for the synthesis of carbaoligosaccharides.