Thiazolidine methylidinemalonate

Cyclization of the thiazolidine methylidinemalonate 684 with PPA gave thiazoloquinoline 3-carboxylate which upon hydrolysis afforded 685 and reaction with A-methylpiperazine or a pyrrolidine derivative gave 686 as antibacterial agent (82EP58392, 85USP4550104) (Scheme 116). 

---