Chiraloxazolines, as their boron enolates derived from various boron triflates, react with aldehydes to give erythro-selectivity (97% + %) with enantiomeric purities of 50–60%. Achiral oxazolines as their boron enolates derived from diisopinocampheylborane give, on reaction with aldehydes, β-hydroxy esters with high threo-selectivity (90+%) in 77–85% ee. A variety of structurally different oxazolines