Linear pentapeptide ester, phthaloyl-bis-[glycylglycine]-OMe, 3, have been prepared via coupling of
N-phthalic acid or dichloride with glycylglycine ester, which was hydrolyzed to the corresponding
acid, phthaloyl-bis-[glycylglycine], 4. Cyclization of tetrapeptide acids to give cyclic pentapeptide
esters, acids and hydrazides. A preliminary cytotoxicity evaluation (National Cancer Institute, Cairo,
EGYPT), for a representative example, Cyclo-(phthaloyl)-)-bis-[glycylglycine]-L-Lys-OMe (phthaloyl
cyclic pentapeptide methyl ester) 5, against eight human cancer cell lines, seemed interesting. The
detailed comparative results with those of five common anticancer drugs and their complementary
biological and biochemical assays, for all the candidates, are envisioned, and will be published