INTER- AND INTRAMOLECULAR TRAPPING OFRADICALS IN Ti(III) MEDIATED OPENING OF CHIRAL 2,3-EPOXY ALCOHOLS: APPLICATIONS IN THE STEREOSELECTIVE SYNTHESES OF QUATERNARY CHIRAL CENTERS, HIGHLY SUBSTITUTED CARBOCYCLES, OXACYCLES, AZACYCLES AND FORMAL TOTAL SYNTHESIS OF (+)-Sch 642305