Experimental And Theoretical Studies On The Synthesis, Structures And Properties Of Guanine Derivatives

One of the highlights in the field of G-tetramers supramolecularchemistry is design and synthesis of novel guanine derivatives andexplores the interaction between these derivatives and metal ions or smallorganic molecules. Due to the unique structure of G-tetramers, they havepotential significance in the aspects of molecular recognition, ionchannels, radioactive waste disposal etc. In this thesis, two series ofguanine derivatives have been synthesized by N9-position fuctionalizedmodification of guanine unit, and studied the correspondingself-assmebly properties. Some related reaction mechanisms have beendiscussed by quantum chemistry and experimental methods. The maincontents in this thesis are shown as follows.1. Guanine as raw material, it was uesd to synthesis N9-positionlipophilic guanine derivatives and different center of the different centralcation of the G-tetramers. Their structures were characterized by1H,13CNMR and ESI-TOF mass spectrometry. Futher studies show that withoutthe influence of external factors (including: the atmosphere,solvents,anions,etc.),the strength of the interaction betweenthe alkali metal ions and the guanine G-tetramer present fundamentaldifference when the center ion is different in the guanine G-tetamer, andthe intensity order: Na~+> Li~+> K~+>Rb~+> Cs~+.2. For synthetizing N9-position lipophilic guanine derivatives, theprevious reports that2-amino-6-chloropurine will be transfer into guaninein acid solution was be used, and the condition is mild and yield is veryhigh, but the reaction mechanism is not clear. So the quantum chemicalcalculation method and experimental research were used to study themechanism of2-amino-6-chloropurine transfer into guanine in acidconditions. Formic acid anion like to attack N7-position in the reactionprocess was be found. So the SN2Ar reaction mechanism formed thecorresponding formic acid ester, but in strong acid conditions, formic acidester easily happened hydrolysis and generating a guanine.3. For guanine alkylation transformation process, some unusualguanine O~6-alkylation phenomenon were be found and making us throughexperiment and quantum chemical calculation method to investigate thereaction mechanism of O6-alkylationguanine. The study found, ketonetype guanine easily through the dimer or by water molecule into enolatetype guanine; Further study showed that enolate type guanine than ketonetype guanine more easy to form guanine anion, and the O6-position ofguanine anion reacted with halogenated hydrocarbon by SN2mechanism, which causes the alkylation.4. Interaction between lipophilic guanine and melamine wascharactered by1D,2D1H NMR. When melamine exists, N1-positionproton of guanine will move to O6-position;Futher study through thetheoretical calculation found that enolate type guanine can tightly bondwith melamine by H-bonds.5.2-amino-6-chloropurine as raw materials, was used to synthetic theN9-(3-sulphur propyl) guanine, then coupling with gold nanoparticles,and guanine@gold nanoparticles was obtained. Investigation the intectionbetween guanine@gold nanoparticles and melamine by UV, the color ofnanoparticles was be changed when solution of melamine added. Theresults show that guanine@gold nanoparticles can detection melaminewhich concentration can low to5μ M.