Enantioselective Synthesis of syn-α,β-Diamino Acid Derivatives

Significance

A catalytic enantioselective ­Mannich reaction of α-isothiocyanato imide (2) with sulfonyl-protected imines 3 has been reported. Using quinidine-derived catalyst 1, syn-α,β-­diamino acid derivatives 4 were obtained in high yields and with high diastereoselectivity and enantioselectivity. When 4-nitrophenylsulfonyl (Ns) protected imines that decrease product inhibition by giving less soluble products 4b were used, catalyst loadings of 0.25 mol% were still highly efficient.