Practical asymmetric access to carboxy-differentiated aspartate derivatives via 1,3-dipolar cycloaddition of a nitrone with (R)-4-ethyl-N-vinyloxazolidin-2-one

A new practical approach to enantioenriched carboxy-differentiated aspartate derivatives was achieved in three steps via the 1,3-dipolar cycloaddition of N-benzyl-α-carbonyloxyethylnitrone with (R)-4-ethyl-N-vinyloxazolidin-2-one and chemoselective nucleophilic displacement of aspartimide under appropriate conditions (racemization less than 3%).

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(S)-1-Ethyl 4-methyl 2-(dibenzylamino)succinateC21H25NO4Ee = 94%[α]D = −76.5 (c 0.39, CHCl3)Absolute configuration: (S)

(S)-1-Ethyl 4-benzyl 2-(dibenzylamino)succinateC27H29NO4Ee = 96%[α]D = −58.2 (c 0.40, CHCl3)Absolute configuration: (S)

(S)-3-(Dibenzylamino)-4-ethoxy-4-oxobutanoic acidC20H23NO4Ee = 96%[α]D = −96.2 (c 0.40, CHCl3)Absolute configuration: (S)

(S)-Ethyl 4-(benzylamino)-2-(dibenzylamino)-4-oxobutanoateC27H30N2O3Ee = 99%[α]D = −79.8 (c 0.54, CHCl3)Absolute configuration: (S)

(S)-Ethyl 4-(butylamino)-2-(dibenzylamino)-4-oxobutanoateC24H32N2O3Ee = 95%[α]D = −79.9 (c 0.46, CHCl3)Absolute configuration: (S)

(S)-Ethyl 2-(dibenzylamino)-4-(methoxy(methyl)amino)-4-oxobutanoateC22H28N2O4Ee = 98%[α]D = −78.2 (c 0.35, CHCl3)Absolute configuration: (S)