Abstract The synthesis and reduction of four new 2-substituted β-keto-ester derivatives (6– 9), employing inexpensive sodium borohydride, were achieved to evaluate the diastereoselectivity of the reduction process of 2-allyl-2-carbomethoxy cyclopentanone derivative (1a) in the same conditions. These results indicating that the diastereoselective control in this process depend on blockage of the re-face of (1a) by a proposed carbonyl-π ...