title: Evaluation of functional analogs of CC-1065 and the duocarmycins incorporating the cross-linking 9a-chloromethyl-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-on e (C2BI) alkylation subunit.
abstract: The DNA alkylation properties and in vitro cytotoxic activity of a series of analogs of CC-1065 and the duocarmycins incorporating the 9a-chloromethyl-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (C2BI) alkylation subunit are detailed. The C2BI-based agents have been shown to alkylate DNA within the minor groove in a fashion analogous to CC-1065 or duocarmycin. The stereoelectronically-controlled adenine N3 addition to the least substituted cyclopropane carbon occurs with a selectivity that represents a composite of the two enantiomers of the corresponding CBI-based agents. Additional high affinity alkylation sites were detected which were not prominent alkylation sites for either enantiomer of the CBI-based agents. Such sites may represent induced high affinity alkylation sites resulting from DNA cross-linking following complementary strand alkylation at a high affinity alkylation site and each such site detected proved consistent with predicted models of an adenine-adenine cross-linking event. Further, consistent with this interpretation, the C2BI agents were shown to constitute efficient cross-linking agents with DNA cross-linking being observed at the same concentrations as DNA alkylation. In comparison to the parent CBI-based agents, the C2BI-based agents proved to be approximately 100-10,000x less effective at DNA alkylation and 100-10,000x less potent in cytotoxic assays. This is suggested to be the consequence of a significant steric deceleration of the adenine N3 alkylation reaction attributable to the additional 9a-chloromethyl substituent. Consistent with this interpretation, the noncovalent binding constant of C2BI-CDPI2 for poly[dA]-poly[dA]-poly[dT] proved nearly identical to that of CDPI3 under kinetic binding conditions, and prolonged incubation of C2BI-CDPI2 with poly[dA]-poly[dT] (72 h, 25 degrees C) provided covalent complexes with a helix stabilization comparable to that observed with (+)- or (-)-CPI-CDPI2 indicating that the size of the C2BI subunit inhibits but does not preclude productive DNA alkylation.
authors.affiliation: Department of Chemistry, Scripps Research Institute, La Jolla, CA 92037.
authors.forename: D L
authors.initials: DL
authors.lastname: Boger
authors.forename: D S
authors.initials: DS
authors.lastname: Johnson
authors.forename: M S
authors.initials: MS
authors.lastname: Palanki
authors.forename: P A
authors.initials: PA
authors.lastname: Kitos
authors.forename: J
authors.initials: J
authors.lastname: Chang
authors.forename: P
authors.initials: P
authors.lastname: Dowell
mesh_terms: D000478:Alkylation; D000903:Antibiotics, Antineoplastic / Q000737:chemistry* / Q000633:toxicity; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D003432:Cross-Linking Reagents; D004247:DNA / Q000737:chemistry; D000080890:Duocarmycins; D004591:Electrophoresis, Polyacrylamide Gel; D007211:Indoles; D007933:Leucomycins / Q000737:chemistry* / Q000633:toxicity; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009691:Nucleic Acid Denaturation; D011760:Pyrrolidinones / Q000737:chemistry
chemical_list: C089335:9a-chloromethyl-1,2,9,9a-tetrahydrocyclopropa(c)benz(e)indol-4-one; D000903:Antibiotics, Antineoplastic; D003432:Cross-Linking Reagents; D000080890:Duocarmycins; D007211:Indoles; D007933:Leucomycins; D011760:Pyrrolidinones; C018782:CC 1065; D004247:DNA; C058289:duocarmycin A