Significance: The authors reported a highly enantioselective and general method toward a-diazo-b-hydroxy esters using catalytic direct aldol reaction of ethyl diazoacetate (EDA). Broad substrate scope, commercial availability of reagents and high concentrations (1 M) at which the reactions are performed makes this method very powerful. Furthermore, the authors demonstrated the utility of the products obtained toward synthesis of carbon and heteroatom substituents with high diastereo-and enantioselectivities.Comment: Although the asymmetric direct aldol reaction constitutes a powerful strategy to the atom-economical synthesis of optically pure compounds, few methods exist for the direct aldol reaction of esters. The Trost group has provided an excellent solution to this challenging problem. Furthermore, they expanded the utility of chiral ligand (S,S)-1, using dinuclear species other than zinc, most notably magnesium. S e l e c t e d e x a m p l e s :Bu 2 Mg (10 mol%) additive (5 mol%) THF, -20 °C OEt O N 2 R H O R OH N 2 OEt O (S,S)-1 (5 mol%) OH Me N N HO Ph Ph OH Ph Ph (S,S)-1 OH OH additive OH N 2 OEt O + slow addition 92% yield, 95% ee OH N 2 OEt O 88% yield, 98% ee OH N 2 OEt O 83% yield, 93% ee Cl MeO OH N 2 OEt O 83% yield, 96% ee O OH N 2 OEt O 50% yield, 97% ee OH N 2 OEt O 50% yield, 94% ee Ph 3 R OH N 2 OEt O Et 3 B, THF, r.t. R OH OEt O 65% yield, 95% ee dr = 14.4:1 DMDO, CH 2 Cl 2 , -35 °C then NaBH 4 , -78 °C R OH OH OEt O 70% yield, 95% ee dr = 21:1 1) TBSCl, imidazole, CH 2 Cl 2 2) Pd(C), H 2 , EtOAc R OH OEt O 82% yield, 84% ee T r a n s f o r m a t i o n o f d i a z o e s t e r : SYNFACTS Contributors: