ELECTROCHEMICAL OXIDATION OF PROLINE DERIVATIVES - TOTAL SYNTHESES OF BULGECININE AND BULGECIN-C

The influence of structure on the efficiency of the electrochemical C-5 oxidation of (2S,4S)-hydroxyproline carbamate esters is presented. Optimum methoxylation was observed with (2S,4S)-4-acetoxy-1,2-pyrrolidine-dicarboxylic acid 2-methyl 1-(2-(trimethylsily)ethyl) ester (19). The corresponding C-5 methoxy derivative 20 was converted into bulgecinine (4) via a stereospecific radical homologation to incorporate the C-5 hydroxymethyl substituent. Bulgecin C (1c) was prepared via a beta-stereoselective glycosidation reaction using a 2-azido-2-deoxy-alpha-D-glucopyranosyl trichloroacetimidate derivative, regiospecific C-4' sulfation, and deprotection.