Takashi Siroi

Chemoselective electrolytic chlorination of methyl group of 3-methyl-3-butenoate moiety of thiazoline-azetidinone homologues

Abstract Chemoselective electrochlorination of the methyl group on the 3-methyl-3-butenoate moiety of thiazoline-azetidinone derivatives derived from penicillins G and V has been performed in a CH 2 Cl 2 -H 2 O-NaCl-H 2 SO 4 -(Pt or C electrodes) system by adjusting the amount of electricity passed as well as the concentration of Cl − in the media.

Penicillin-cephalosporin conversion III. A Novel route to 3-chloromethyl-Δ3-cephems

Abstract Synthesis of 3-chloromethyl-Δ 3 -cephems 3 from 4-arenesulfonylthioazetidin-2-ones 1 , derived from penicillins G and V, has been achieved by the electrolytic ene-type chlorination of 1 in a CHC1 3 -aqueous NaCl-H 2 SO 4 -(Pt electrodes) system and subsequent ring closure with NH 3 in DMF.

Penicillin-cephalosporin conversion IV. Direct synthesis of 3'-thiosubstituted cephalosporins from thiazoline-azetidinones

Direct transformation of thiazoline-azetidinones 2, derived from penicillin G and V, into 3′-thio-substituted cephalosporins 4 has been performed by ring opening of the thiazoline moiety with sulfenyl chlorides followed by ring closure with NH3 in dimethylformamide and simultaneous displacement of the allylic chlorine atom with the leaving thiolates.

Penicillin-cephalosporin conversion X. New synthesis of dithioazetidinones from thiazoline-azetidinones

Abstract New ring-opening reaction of thiazoline-azetidinones 1 to dithioazetidinones 2 was achieved with 2-benzothiazolyl disulfide in aqueous acidic media and its potentiality for the preparation of a variety of cephalosporins 3 from various thiazoline-azetidinones 1 is demonstrated.

Penicillin-cephalosporin conversion. XI: Synthesis of 7-(α-substituted phenylacetoamide)cephalosporins by utilization of all the framework elements of penicillin G

Abstract A successful synthesis of clinically significant cephalosporins 2a-c with use of all the framework elements of penicillin G is described.