Synthesis of the four stereoisomers of several 3‐(1‐aminoethyl)pyrrolidines. Important intermediates in the preparation of quinolone antibacterials

The use of S ‐α‐methylbenzyl as a chiral auxiliary at N 1 allowed separation of diastereomeric 2‐pyrrolidinones substituted with an ester, ketoester, ketone and oxime at the C 4 position. Reduction of each diastereomer of 4‐[1‐(hydroxyimino)ethyl]‐1‐(1‐phenylethyl)‐2‐pyrrolidinone, 10s and 10r , provided a pair of epimeric amines, [ 11sr and 11ss ] and [ 11rs and 11rr ], that were separated by chromatography. The four stereoisomers of 4‐(1‐aminoethyl)‐1‐(1‐phenylethyl)‐2‐pyrrolidinone, 11 , were elaborated into several stereochemically pure 3‐(1‐aminoethyl)pyrrolidines, 1 and 15‐23 . These compounds are useful intermediates (C 7 side chains) for quinolone antibacterials.