Crystals of the chiral malic acid hydrate (C_4H_6O_5·H_2O) were unexpectedlyobtained from an ethanol/water solution containing racemic D, L-malic acid and L-asparagine. Thecrystal belongs to orthorhombic space gr...Crystals of the chiral malic acid hydrate (C_4H_6O_5·H_2O) were unexpectedlyobtained from an ethanol/water solution containing racemic D, L-malic acid and L-asparagine. Thecrystal belongs to orthorhombic space group P2_12_12_1 with cell dimensions of a = 0.5576(1), b =0.9818(2), c = 1.1793(2) nm, V = 0.6455(2) nm^3, Z = 4, μ(Mo K_a) =0.152 mm^(-1), F(000) = 320, D_c= 1.565 g·cm^(-3), R=0.051, wR = 0.136 for 657 observed reflections [ I > 2σ(I) ]. Thesignificant difference in bond distances for carboxyl groups suggests that the crystal consist ofmalate anion and protonized crystalline water. This is a report for direct separation of racemicmixture, i.e., without the formation of a molecular complex of raceme with a chiral separatingreagent.展开更多
A flexible approach to ethyl (3R,4S)-N-Boc-4-amino-3-hy-droxy-5-phenyIpentanoate (N-Boc-AHPPA-OEt), the γ-amino-β-hydroxy add moiety of hapalosin is described. The synthetic method features a ring-opening ethanolysi...A flexible approach to ethyl (3R,4S)-N-Boc-4-amino-3-hy-droxy-5-phenyIpentanoate (N-Boc-AHPPA-OEt), the γ-amino-β-hydroxy add moiety of hapalosin is described. The synthetic method features a ring-opening ethanolysis of an activated N-Boc-lactam, which is obtained via a diastereoselective reductive-alkylation of (R)-malimide derivative. The flexibility of the method resides hi the introduction of the alkyl side chain by Grignard reagent addition.展开更多
文摘Crystals of the chiral malic acid hydrate (C_4H_6O_5·H_2O) were unexpectedlyobtained from an ethanol/water solution containing racemic D, L-malic acid and L-asparagine. Thecrystal belongs to orthorhombic space group P2_12_12_1 with cell dimensions of a = 0.5576(1), b =0.9818(2), c = 1.1793(2) nm, V = 0.6455(2) nm^3, Z = 4, μ(Mo K_a) =0.152 mm^(-1), F(000) = 320, D_c= 1.565 g·cm^(-3), R=0.051, wR = 0.136 for 657 observed reflections [ I > 2σ(I) ]. Thesignificant difference in bond distances for carboxyl groups suggests that the crystal consist ofmalate anion and protonized crystalline water. This is a report for direct separation of racemicmixture, i.e., without the formation of a molecular complex of raceme with a chiral separatingreagent.
基金Project supported by the National Science Foundation for Distinguished Young Investigators,the National Natural Science Foundation of China and the Fund for doctoral sites of the Ministry of Education.
文摘A flexible approach to ethyl (3R,4S)-N-Boc-4-amino-3-hy-droxy-5-phenyIpentanoate (N-Boc-AHPPA-OEt), the γ-amino-β-hydroxy add moiety of hapalosin is described. The synthetic method features a ring-opening ethanolysis of an activated N-Boc-lactam, which is obtained via a diastereoselective reductive-alkylation of (R)-malimide derivative. The flexibility of the method resides hi the introduction of the alkyl side chain by Grignard reagent addition.
