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Cephalosporin 7-sulfenylated

N-Allenylazetidinone 181 rearranges to cephalosporin 182 in the presence of lithium chloride (Eq. 13.62) [70], This is a very unusual reaction that is presumed to be initiated by chloride ion-induced cleavage of the disulfide to give sulfenyl chloride 183. Thiolate attack at the allene sp carbon atom of 183 generates ester enolate 184, which cyclizes to 182. The reactivity of the allene function in 181 ensures the success of the reaction. [Pg.843]

Most of the clinically significant cephalosporin antibiotics possess a sulfenyl group at the C-3 position. The electrolytic ene-type chlorination products 2 are potent intermediates for the synthesis of 3 -substituted cephalosporins 6 (Scheme 2-2)8). [Pg.157]

Direct transformation of thiazoline-azetidinones 2 into 3 -thio-substituted cephalosporins 6 has been performed by ring opening of the thiazoline moiety with sulfenyl chloride followed by ring closure with ammonia in dimethylformamide and simultaneous displacement of the allylic chlorine atom with the leaving thiolates. [Pg.158]

Direct transformation of a/p/w-aminoalkanoates 27 to the corresponding sulfenimines 29 by electrolysis with disulfide 28 in a CHjCyHjO—MgBr2—(Pt) system has been developed (Scheme 2-9)22). The procedure can be applied to the sulfenylation of C-6/C-7 amino groups of penicillins and cephalosporins 30 (Scheme 2-10). [Pg.163]

In general, none of the 7(6)-alkylated (acylated) cephalosporins or penicillins reported showed enhanced biological activity relative to their unsubstituted parents. These disappointing results, coupled with the concomitant discovery of cephamycins, led researchers to explore the latter more promising area. Among the earliest methods employed for 7(6)-methoxyl introduction was initial -lactam sulfenylation or halogenation,... [Pg.278]

Gordon, E. M., H. W. Chang, and C. M. Cimarusti Sulfenyl Transfer Rearrangement of Thiooximes. A Novel Conversion of Cephalosporins to 7a-Methoxycephalosporins. J. Amer. Chem. Soc. 99, 5504 (1977). [Pg.99]


See other pages where Cephalosporin 7-sulfenylated is mentioned: [Pg.314]    [Pg.314]    [Pg.164]    [Pg.261]    [Pg.261]    [Pg.280]   
See also in sourсe #XX -- [ Pg.280 ]




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