Preformed Li enolates of hindered aryl esters condense with aldehydes to give predominantly threo aldols. The method has been explored with esters 3 (DMP propionate), 4 (BHT propionate), and 5 (DBHA propionate). DMP propionate reacts with benzaldehyde and α-unbranched aliphatic aldehydes to give threo: erythro ratios of about 6.5: 1. However, with α-branched aliphatic aldehydes, ester 3 gives only threo-aldols. BHT propionate and ...