Microgel supported hydantoins as new chiral auxiliaries for asymmetric Mannich reactions

Four distinct microgel supported hydantoin chiral auxiliaries were prepared with four different cross-linkers and evaluated in asymmetric Mannich reactions, which proceeded in good chemical yields and with excellent stereoselectivities. Moreover, the microgel supported hydantoin chiral auxiliaries could be reused for at least four cycles without an appreciable reduction in the yield or stereoselectivity.

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(2R,3S)-Methyl 2-methyl-3-(p-methoxyphenylamino)-3-phenylpropanoateC18H21NO3[α]D20 = −48.7 (c 0.96, CH2Cl2)Absolute configuration: (2R,3S)Source of chirality: chiral auxiliary induced Mannich reactions

(2R,3S)-Methyl 2-methyl-3-(p-methoxyphenylamino)-3-(p-chloro-phenyl) propanoateC18H20ClNO3[α]D20 = −44.6 (c 0.85, CH2Cl2)Absolute configuration: (2R,3S)Source of chirality: chiral auxiliary induced Mannich reactions

(2R,3S)-Methyl 2-methyl-3-(p-methoxyphenylamino)-3-(m-nitro-phenyl) propanoateC18H20N2O5[α]D20 = −47.9 (c 1.12, CH2Cl2)Absolute configuration: (2R,3S)Source of chirality: chiral auxiliary induced Mannich reactions

(2R,3S)-Methyl 2-methyl-3-(p-methoxyphenylamino)-3-(2′,3′-dimethoxyphenyl) propanoateC20H25NO5[α]D20 = −50.7 (c 1.08, CH2Cl2)Absolute configuration: (2R,3S)Source of chirality: chiral auxiliary induced Mannich reactions

(2R,3S)-Methyl 2-methyl-3-(p-methoxyphenylamino)-3-(2′-furyl)-propanoateC16H19NO4[α]D20 = −47.8 (c 1.10, CH2Cl2)Absolute configuration: (2R,3S)Source of chirality: chiral auxiliary induced Mannich reactions

(2R,3S)-Methyl 2-methyl-3-(p-methoxyphenylamino)-3-(2′-thienyl)-propanoateC16H19NO3S[α]D20 = −45.1 (c 1.24, CH2Cl2)Absolute configuration: (2R,3S)Source of chirality: chiral auxiliary induced Mannich reactions