Abstract: From γ-butyrolactone 1, we synthesized (S)-2-methyl-2-nitroethenyl butyrolactone (S)-3 by the mean of direct enantioselective construction of molecule with quaternary carbon stereocenter on the bases of our previous research. (S)-3 was obtained in₃₆% overall yield with 94% optical purity. We established a set of conversions from(±)-3 to the precursor of Vitamin B₁₂ ring Bimide 8 under mild conditions and complete the synthesis of three derivatives of ethosuximide 6_ 8 at the same time. By remolding TiCl₃ reduction of nitroolefins the yield of 2-methyl butyrolactone-2-acetaldehyde 4 from 3 can be increased to 88%. Anew method has been found to directly construct succinimide ring from 2-methyl butyrolactone-3-acetic acid 5. The procedure of this conversion is DCCcondensation of 5 and dry benzylamine in acetonitrile catalyzed by DMAPat 0 ℃ over night.

Key words: Chiral quaternary carbon, Vitamin B₁₂ ring-B imide, Succinimide