Dimethylpyridin-4-ylamine-Catalysed Alcoholysis of 2-Amino-N,N,N-Trimethyl-9H-purine-6-ylammonium Chloride: An Effective Route to O6-Substituted Guanine Derivatives from Alcohols with Poor Nucleophilicity
Dimethylpyridin-4-ylamine (DMAP)-catalysed reactions of 2-amino-N,N,N-trimethyl-9H-purine-6-ylammonium chloride with fluoropyridine methoxides and various other alkoxides in DMSO at 60 °C gave the corresponding coupling products in moderate to good yields between 20-87%. Under these reaction conditions, fluorinated O 6 -substituted Guanine derivatives have been synthesized which could not be obtained via known analogous literature procedures. The respective yields of known O 6 -substituted guanine derivatives could be significantly improved by using this method. The efficient use of DMAP as an excellent nucleophilic catalyst in the syntheses of O 6 -substituted Guanine derivatives has thus …
Application of tris-allyl-DOTA in the preparation of DOTA–peptide conjugates
Abstract The synthesis of tris-allyl-DOTA starting from cyclen and its application in the preparation of DOTA–peptide conjugates is reported. Clinically important conjugates such as DOTA–Tyr3-octreotide (DOTA–TOC), DOTA–Tyr3-octreotate (DOTA–TATE) as well as a DOTA–RGD peptide were synthesized in high yields with Fmoc solid phase peptide synthesis. The final, extremely reliable de-allylation was achieved on solid phase by different methods identifying morpholine/Pd(0) as the most suitable one obtaining all DOTA peptide conjugates in high yields. All DOTA–peptides were purified by reversed phase HPLC and structural identity was proved using MALDI-TOF mass spectrometry.
18F-labeling of peptides by means of an organosilicon-based fluoride acceptor.
Fluorine-18 is among the most commonly used radionuclides for positron emission tomography (PET). This non-invasive imaging technique is capable of providing in vivo information about the distribution of radiolabeled biomolecules by 1808 coincidence detection of two simultaneously emitted photons from positron–electron annihilation. Although a number of different radiotracers have been successfully employed in PET, only a few, such as 2-[F]fluoro-2-deoxy-d-glucose (FDG) and [F]fluorodopa, have gained widespread application in nuclear medicine. The reason for this is that the regioselective introduction of F into tracer molecules is often non-specific and radiochemical yields (RCY) of the Fl…