Xiaoping Cao

Stereoselective synthesis of substituted all-trans 1,3,5,7-octatetraenes by a modified Ramberg–Bäcklund reaction

Abstract The reaction of allylic dienylic sulfone with dibromodifluoromethane in the presence of alumina-supported KOH in dichloromethane solution results in facile rearrangement affording the corresponding all- trans 1,3,5,7-octatetraenes in excellent yields. This result shows that the double bonds of stereochemically defined allylic dienylic sulfone retain their stereochemistry and the newly formed double bond has an ( E )-configuration in the modified Ramberg–Backlund procedure.

Synthesis and DNA-recognition and -cleavage properties of multiply charged porphyrin esters.

A series of systematically modified porphyrin esters, compounds 1–6, with multiple, permanent positive charges introduced at the meso‐positions via N‐methylated 4‐, 3‐, or 2‐pyridyl moieties, were prepared and characterized. Their singlet‐oxygen production, CT‐DNA‐binding properties, and plasmid‐DNA photocleavage propensities were determined spectroscopically and by gel electrophoresis, and compared to those of the known, fourfold‐charged parent porphyrin 4,4′,4″,4′′′‐porphyrin‐5,10,15,20‐tetrayltetrakis(1‐methylpyridinium) (TMPyP4). Some interesting structure–activity relationships could be established to rationalize effects affecting DNA binding mode and cleavage ability.