Studies related to penicillins. Part I. 6-α-Chloropenicillanic acid and its reaction with nucleophiles
The preparation of 6-α-chloropenicillanic acid from the deamination of 6-β-aminopenicillanic acid has been improved, and the reaction is shown to proceed by way of 6-azopenicillanic acid. Benzyl 6-azopenicillanate has been isolated from the reaction of benzyl 6-β-aminopenicillanate with nitrous acid. Methyl 6-α-chloropenicillanate is rearranged to 6-azidocarbonyl-2,3-dihydro-3S-methoxycarbonyl-2,2-dimethyl-1,4-thiazine with sodium azide in NN-dimethylformamide and to 2,3-dihydro-3S,6-dimethoxycarbonyl-2,2-dimethyl-1,4-thiazine with methanolic sodium methoxide. 6-α-Chloropenicillanic acid undergoes similar rearrangements.