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Synthetic calicheamicin oligosaccharide derivatives were designed fro pyrimidine recognition.

Research is presented demonstrating the development of a synthetic unified route to 3-hex-en-1,5-diynes. The method is used to synthesize cyclic and linear enediynes.

Two related methods to synthesize (plus or minus)-calicheamicinone, the aglycon of the calicheamicin antitumor antibiotic, are reported. Both compounds represent difficult synthetic targets and are of interest with regard to the mode of action of enediyne antitumor agents. The syntheses showed high levels of steroselectivity and that a calicheamicinone of unnatural stereochemistry may be more efficient at producing double strand cuts in DNA, than natural stereochemical material.

Previous research has shown that the calicheamicin oligosaccharide domain exhibits impressive binding properties. To determine the structural basis for this ability, nuclear magnetic resonance spectroscopy and molecular dynamics calculations are used to solve the solution structure of the 1:1 complex between the head-to-head dimer and the oligonucleotide d2. Results indicate that carbohydrates can be useful in generating DNA target specificity and may control the behavior of nucleic acids.

The binding affinity between calicheamicin and a single TCCT.AGGA site within a synthetic duplex DNA is measured by kinetic analysis. DNA binding affinity of the carbohydrate domain is analyzed by competitive binding analysis involving calicheamicin and the calicheamicin oligosaccharide. Iodine substituent on the aromatic ring of the carbohydrate domain interacts with the exocyclic C2-NH2 group or both guanine residues at the target site.

Duplex d(GCATCCTAGC).d(GCTAGGATGC) reacts with calicheamicin and calicheamicin oligosaccharide domain to produce two complexes. NMR spectroscopic analyses show that the oligosaccharide domain of calicheamicin influences binding and sequence recognition in the DNA microgroove. Two species identified in the NMR spectra imply two different binding modes which permit each radical to reach and abstract its target. A structural model for the calicheamicin complex is derived by molecular dynamics calculation.

The calicheamicin gamma1 and glutathione reaction in the presence of double-stranded DNA yields four products generated by S-S bond exchange. The calicheamicin gamma1 bisulfide group and glutathione thiol function react to give the S-S bond product. There is no evidence of DNA catalysis of thiol function in water.

The enantioselective total synthesis of the naturally occurring antipode of the calicheamicin aglycon, (-)-calicheamicinone, was accomplished. An intramolecular 1,3-dipolar cycloaddition reaction of an alkynyl nitrite oxide was used to incorporate the nitrogen atom of the urethane. Asymmetry was introduced into the molecule through an asymmetric allylboration reaction. The intramolecular alkylation of an aldehyde was used to bridge the enediyne residue.

Schmidt's trichloroacetimidate procedure was used to achieve the stereoselective glycosidation, which combined the suitably functionalized aglycon 3 with the oligosaccharide fragment 2, in the first total synthesis of calicheamicin gamma (sub 1)(super I). The required alcoxylamine 32 and its A-4 isomer 32-epi were produced by the stereoselective reduction of oxime 31, obtained from the coupling product, with NACNBH3 in the presence of BF3.OEt2, during the synthetic process.

The calicheamicin gamma (sub 1)(super I) oligosaccharide portion was totally synthesized for the first time in the form of its methyl glycoside. The stereochemical difficulties associated with a (3,3)-sigmatropic realignment of an allylic thionoimidazolide, were overcome by the easy identification and examination of the synthetic challenge of the B-ring.

The bicyclo(7.3. 1)tridecenediyne core structure of the antitumor antibiotics esperamicin and calicheamicin can be constructed via the complexation of the 10,11-acetylenic bond as its derived eta2 Co(CO)6 adduct. This complexation results in the cation being aligned axially to the enol pi-system in the cyclohexanone ring, with the products unable to undergo cycloaromatization. Cyclohexane-1,2-dione yields 13-ketobicyclo(7.3.1)tridecenediyne in ten steps. The Co2(CO)6-eta2 propargylic cation methodology may also be used in the preparation of the core structures of dynemicin and neocarzinostatin.

The 13-ketobicylco(7.3.1)tridecenediyne core structure of calicheamicin and esperamicin is reported. The core structure is functionalized in a sequential, oxidative manner, which allows the insertion of the 1,2 double bond and 3-oxygen substitution. The 4beta-hydroxyl substituent allows the intramolecular introduction of the nitrogen functionality at C2. However, the cyclic carbamate formed is too resistant to hydrolysis to be of any synthetic use. Allylic trisulfide may be attached to the 13-keto moiety by Wittig chemistry.

Degradation and spectroscopic studies are performed to elucidate the chemical structure of the antitumor antibiotic calicheamicin gamma1. The structural assignment of the glycosidic chain results from the methanolysis studies on calicheamicin gamma1 and N-acetylcalicheamicin gamma1. Chemical and spectroscopic evidence support the enediyne structure of calicheamicinone the existence of a 1,4-dehydrobenzene diradical as a reaction intermediate. The enediyne system is revealed to be a major determinant of the DNA-damaging capabilities of the calicheamicins.

A conceptual different approach to the synthesis of calicheamicinone is discussed. The approach is based on the intramolecular alkenyl nitrile oxide dipolar cycloaddition reaction which leads to the incorporation of the full functionality of the agyclon and which agrees with enantioselective synthesis. The methodology offers an easy access to the study of the calicheamicin- and esperamicin-type aglycon skeletons in their optically active forms.

Calicheamicin-homeodomain conjugate is found to be an effective sequence-specific DNA cleavage and mapping tool.

A gene (calC) from Micromonospora echinospora has been discovered and characterized.

Experiments were performed to synthesize a 10-membered enediyne ring based on an eta2Co2(CO)6-propargylic aldol cyclization. Commercially available 5-methoxysalicylic acid was used to prepare the phenol in four standard steps. The preparation of aglycon calicheamicinone from 5-methoxysalicylic acid obtained 1.4% overall yield at an average of 86% per step. Although the route described was the most efficient synthesis performed, modification of the method to provide an enantioselective synthesis can be done by the application of asymmetric induction methodology.

Calicheamicin oligosaccharide dimeric forms are synthesized for a molecular recognition program in biological systems. Specific, high-affinity binding of the two variables to specific duplex DNA sequences are established through competitive bidding experiments. Oligosaccharide-DNA interactions displayed characteristic site selectivities that indicated need for additional research on DNA attachments and related issues.

Calicheamicin gamma1 I was complexed to different recognition sites and studied.