M icrobes employ several catalytic strategies to transform conformationally f lexible peptide chains into rigidified scaffolds that possess antibiotic or toxin activity. Prominent examples include the biosynthesis of the -lactam antibiotics of the penicillin and cephalosporin families (1) and the maturation of vancomycin (2) where distinct structural modifications to the nascent peptide chains ...

New pyrimido [4, 5-e] [1, 3, 4]thia- diazin-7-yl] hydrazines were synthesized via the cyclocondensation of alkyl-2-phenylhydrazinecarbodithioates as a binucleophile with 5-bromo-2,4-dichloro-6-methylpyrimidine as a bielectrophile , and replacement of C-7 chloro atom by hydrazine in ethanol as the solvent . This method has advantages over methods currently described in the literature for the con...

New 1,5-tetra alkyl methyl- phenyl-1H-pyrimido[4,5-e][1,3,4]thiadiazine-3,7-diamine  were synthesized via the cyclocondensation of 2-(5-bromo-2-chloro-6-methylpyrimidin-4-yl)-2-methylhydrazine with phenylthioisothiocyanate  and further replacement of chlorine atom on the seven number position of pyrimido[4, 5- e][1, 3, 4]thiadiazin by appropriate secondary amines  in simple and efficient methods. 

New 1,5-tetra alkyl methyl- phenyl-1H-pyrimido[4,5-e][1,3,4]thiadiazine-3,7-diamine were synthesized via the cyclocondensation of 2-(5-bromo-2-chloro-6-methylpyrimidin-4-yl)-2-methylhydrazine with phenylthioisothiocyanate and further replacement of chlorine atom on the seven number position of pyrimido[4, 5- e][1, 3, 4]thiadiazin by appropriate secondary amines in simple and efficient methods.

The fields of natural product total synthesis and combinatorial chemistry have major differences as well as much in common. Unique to combinatorial chemistry is the need to devise rapid and efficient methods for parallel synthesis and purification, while an area of overlap is the targeting of natural product scaffolds for combinatorial libraries. Both these aspects are illustrated with examples...