The alkylation of the chiral2-cyano-6-oxazolopipridine synthon (1) with the iodo ketal 2 gave, after selective cleavage of the cyano group, the oxazolopiperidine 4 having the 2s configuration. Compound 4 was alkylated with CH3MgI, giving a 4 1 mixture of alcohols 6 and 7 in which the major product 6 possessed the desired 2, 6-cis configuration. Treatment of 6 under acidic hydrogenation conditions (H2, Pd/C, H+) led to the desired (-)- ...
