Abstract Reaction of 2 (3, 4)-pyridinecarboxaldehydes (5) with ethylidenetriphenylphosphorane afford a mixture of stereoisomers Z-(6) and E-1-[2 (3, 4)- pyridinyl]-1-propenes (7). m-Chloroperbenzoic acid oxidation of 6 and 7 yields a 60: 40 mixture of Z-(8) and E-1-[1-oxido-2 (3, 4)-pyridinyl]-2-methyloxiranes (9). The regiospecific reaction of Z-isomers 8a-c with cyclic amines as piperidine give rise to threo-1-hydroxy-1-[ ...