Abstract
I. Study of Photo-induced DNA Cleavages by an AzulenequinoneII. Development of Ceric Ammoninum Nitrate as a Selective Deprotecting ReagentAbstract In this dissertation, I report new and controllable photo-induced DNA cleaving processes by use of an azulenequinone under aerobic conditions. I also report the DNA cleavage pattern resulting from this compound under photolytical conditions. Furthermore, silica gel–supported ceric ammonium nitrate was found effective for rapid and selective cleavage of tert-butyldimethylsilyl, triisopropylsilyl, and tert-butoxycarbonyl group from protected compounds. In the first part, a series of single- and double-stranded oligodeoxyribonucleotides were synthesized. These oligodeoxyribonucleotides were cleaved by 3-(p-tolylamino)-1,5-azulenequinone upon irradiation with 350-nm UV light. The single strands were cleaved more efficiently than the double-helices. For the helices containing a deoxyguanosine residue at a bulge, at a hairpin loop, or towards the end, the cleaving efficiency was increased. Based on the DNA substrates studied, the results indicate that 3-(p-tolylamino)-1,5-azulenequinone can detect the abnormal DNA base pairing arrangements and conformations. In the second part, four new methods involving the use of ceric ammonium nitrate (i.e., (Ce(NH4)2(NO3)6) were developed for selective removal of the tert-butyldimethylsilyl or the triisopropylsilyl group from a primary hydroxyl functionality in di- or trisilyl ethers of ribonucleosides and selective removal of the tert-butoxycarbonyl group from an amino, hydroxy, or mercapto functionality in organic compounds. A comparative study of deprotection reactions by utilization of CAN alone or CAN impregnated on silica gel indicates a remarkable increase in the rate of the reaction involving a solid support. The mechanism of electron-transfer processes is proposed for the use of CAN–SiO2 in the removal of these protective groups from organic molecules.