NEW CHIRAL BUILDING-BLOCKS FROM 1,2-5,6-DI-O-ISOPROPYLIDENE-D-MANNITOL - SYNTHESIS OF C-2-SYMMETRICAL AND UNSYMMETRICAL MONOSEPOXIDES AND BISEPOXIDES AND OF A POLYHYDROXYLATED BUTENOLIDE

The enantiopure epoxides 2-6 were synthesized from 1,2;5,6-di-O-isopro pylidene-D-mannitol (1). The terminal epoxides 2 and 3 are available f rom the desoxy mannitol 9 in three steps. The C2-symmetrical epoxides 4 and 5 were generated via the C-4-inverted alcohol 15. The C2-symmetr ical bisepoxide 6 was prepared in a short sequence maintaining the sym metry throughout the entire synthesis. The crystalline butenolide 44 w as prepared in five steps from 1 by Wittig olefination and lactonizati on.