ABSOLUTE ASYMMETRIC-SYNTHESIS FROM ACHIRAL MOLECULES IN THE CHIRAL CRYSTALLINE ENVIRONMENT

The current status of absolute asymmetric synthesis in a chiral crysta lline environment has been reviewed. A number of topochemically contro lled four-center type photocycloadditions are described for a series o f unsymmetrically substituted diolefin crystals and CT crystals. This concept has been applied to intramolecular photoreactions, and several successful absolute asymmetric syntheses have been achieved, involvin g Norrish Type II reaction, di-pi-methane rearrangement, electrocycliz ation, thietane formation, oxetane formation, hydrogen abstraction by thiocarbonyl and alkenyl groups, and radical-pair intermediates.