Novel and artificial enediyne DNA cleaving molecules: molecular design, chemical synthesis, and evaluation

The molecular design and chemical synthesis of novel and artificial enediyne classes of DNA cleaving molecules 1 approx.4, and their chemical and DNA cleaving profiles are described. The enediyne sulfides 1aapprox.1 were synthesized via the coupling of the vinyl iodide 8 and the protected propargyl alcohol 9, and the intramolecular cyclization of the dibromide 17. 1b was found to cycloaromatize by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in 1,4-cyclohexadiene through radical pathways and by a hydroxy anion in dimethyl sulfoxide-Tris-HCl-pH 8.5 buffer through a polar pathway. 1aapprox.1 cleaved DNA under weakly alkaline conditions, and 1e, 1k and 1l, all of which have a DNA intercalatable moiety, exhibited strong DNA cleaving activities with the identical high purine base (G>A) selectivity. The enediyne triols 2a approx. c were prepared from xylitol (19) via the conversion of the keto-aldehyde 24 into the keto-enediyne 25 by an intramolecular aldol reaction. 2a was also cycloaromatized in a manner similar to that for the enediyne sulfide, and 2a approx.c showed guanine-specific DNA cleavages under weakly alkaline conditions. The enynallene sulfones 3a approx. f were obtained by m-CPBA oxidation of the corresponding enediyne sulfides. 3c was cycloaromatized by DBU through both radical and polar pathways. 3a approx.f cleaved DNA at any DNA-base site under weakly alkaline conditions, and 3d approx.f possessing a hydrophilic moiety exhibited stronger DNA cleavages. The dienediynes 4a approx.c were synthesized from 25. 4 c possessing acetoxy groups at the propargylic positions was cycloaromatized by methyl thioglycolate through radical pathways, and cleaved DNA at any pH with guanine-base selectivity. Furthermore, the DNA cleaving activity of 4c significantly increased in the presence of methyl thioglycolate.