Synthesis of (2RS,E)-3-Ethylidene-azetidine-2-carboxylic acid (rac. polyoximic acid)

Article abstract of DOI:10.1016/S0040-4020(01)88257-0

Treatment of α-diazo β-ketoester 4 with a catalytic amount of rhodium (II) acetate followed by Wittig reaction with phosphorane 5 gave the isomeric phenylthioester derivative 6a and 6b. Reduction of 6a led to the corresponding allylic alcohol 7, which was further converted into the bromide 8. Dehalogenation of 8 with NaBH₄/ DMF resulted in compound 9, which was deprotected with trifluoroacetic acid, giving racemic polyoximic acid (1).