Synthesis of hydroxypiperidines using 1,4-ditosyltetrahydropyridines

Dihydroxylation of diastereomerically pure 2-alkyl 1,4-ditosyl-1,2,3,4-tetr ahydropyridines occurs with complete stereoselectivity to give the correspo nding diols. Upon treatment with nucleophile-Lewis acid mixtures the derive d diacetates undergo substitution reactions whose selectivity varies accord ing to the steric bulk of the alkyl substituent.