Highly efficient photochemical synthesis of the enediyne functionality via a Norrish type II reaction

Photoisomerization as a trigger for Bergman cyclization: Synthesis and reactivity of azoenediynes

Cyclic enediynes 1a and 2a containing stable E-azo moiety (azoenediynes) have been synthesized. These compounds upon irradiation with long wavelength UV isomerize to the Z-compounds 1b and 2b, which can be thermally reisomerized to the Z compounds. Reactivity studies toward BC using DSC predictably indicate higher reactivity for the Z-isomers. Our studies may provide a novel way to modulate the reactivity of enediynes under thermal or photochemical conditions.

Synthesis of 9-membered masked enediyne analogues possessing DNA intercalator and sugar moieties

Syntheses of hybrid DNA cleaving molecules which have the 9-membered enediyne structure of kedarcidin with the DNA intercalator of NCS and/or the sugar moieties were accomplished. Introduction of the sugar moieties to the masked enediyne was achieved via S-alkylation of a bromoacetate derivative with a sugar-containing thiol without the need for protection of the sugar moiety.

Synthesis of Bicyclic Enediynes from Bis[phenyl[(trifluoromethanesulfonyl)oxy]iodo]acetylene: A Tandem Diels-Alder/Palladium(II)- and Copper(I)-Cocatalyzed Cross-Coupling Approach

The reaction of bicycloalkenylbis(phenyliodonium) triflates 1a or b (available via the Diels-Alder reaction of bis[phenyl[(trifluoromethanesulfonyl)oxy]iodo]acetylene with cyclopentadiene or furan, respectively) with alkynylstannanes 2a-g at room temperature in DMF in the presence of catalytic amounts of trans-benzyl(chloro)bis(triphenylphosphine)palladium(II) and copper(I) iodide proceeds smoothly and with selectivity to afford good to excellent yields of bicyclic enediynes 3a-k.

Controlled Acceleration and Inhibition of Bergman Cyclization by Metal Chlorides

The Bergman cyclization has been the subject of renewed interest with the discovery of naturally occurring enediyne-based antitumor agents that cleave DNA by means of an aromatic diradical. These natural substrates have a means to trigger this cycloaromatization process. Control of this reaction by substrate modification would allow aromatic diradicals to be generated selectively. In the studies presented here it is disclosed that the Bergman cyclization of 1,2-bis(diphenyl phosphinoethynyl) benzene was accelerated by a factor of >30,000 by the addition of palladium(II) chloride or platinum(II) chloride and was inhibited by the addition of mercury(II) chloride.