Sulfinyldiacetic acid amide ester rac-1 was efficiently synthesized starting from thiodiacetic acid 4. Treatment was rac-1 with Ac2O and TMSOTf in CH2Cl2 at -40degreesC gave chemoselectively amide site alpha-acetoxy sulfide rac-2 in a ratio (91:9) of rac-2 and rac-3 and in a 90% total yield. Similar treatment of 1 with Ac2O and TMSOTf in DMF at room temperature furnished ester site alpha-acetoxy sulfide rac-3 in a highly chemoselective manner (rac-2:rac-3 = 3:97) and in a 92% total yield. (C) 2002 Elsevier Science Ltd. All rights reserved.
Synthesis of New Chiral Sulfinyldiacetic Acid Derivatives and Attempt at Chemoselective Asymmetric Pummerer Reaction.
of sulfinyldiacetic acid dimethyl ester (8) which was derived from thiodiacetic acid (7). (R(S))-1 (99% ee) and (S(S))-1 (99% ee) were readily obtained by methanolysis of (R(S),S)-12 and (S(S),S)-12 with MeONa in MeOH. (R(S),S)-12 and (S(S),S)-12 were furnished by chromatographic separation of the diastereomeric mixture, obtained by oxidation of thiodiacetic mono-carboxylic acid (11) with 30% H2O2 followed