He guanine to a diaminopurine. For this reason, the phosphoramidite is provided with the UltraMILD protecting group, iPr-Pac, to facilitate UltraMILD synthesis and deprotection. Possibly due to steric hindrance from the DEACM, deprotection of the iPr-Pac group requires more time. For a 7 nt sequence with a single insertion of DEACM-dG, deprotection required three and six hours, respectively, for ammonium
hydroxide and potassium carbonate (50 mM in MeOH). For a 12 nt sequence with three insertions, both conditions required overnight treatment. In all cases, the potassium carbonate treatment always gave cleaner chromatograms. Therefore, in general use, an UltraMILD synthesis and potassium carbonate deprotection (50 mM in MeOH) for 6-17 h at room temperature is recommended. Those who prefer a standard synthesis can still obtain relatively good results by using ammonium hydroxide at room temperature overnight (dmf-dG required) or AMA at room temperature for two hours (Ac-dC required) for deprotection.18883-66-4 Description Heat should be avoided, both during deprotection and processing.247062-33-5 Synonym We also found that the DEACM group is relatively stable to ambient lighting.PMID:29261911 We placed aliquots of the yellow phosphoramidite solid in the lab exposed to standard fluorescent lighting during the
day and subsequently analyzed solutions of them by reverse phase HPLC. We found that the purity of the phosphoramidite was reduced by only 0.4 % per day over a three day period. Even though DEACM can be released with visible light, we will fortunately not have to work in the dark. We would like to thank Dr. Heckel and his team for their excellent overview of DEACM-dG, their scientific input as well as their review of this article.
Application Note: Phosphorodithioates in Oligonucleotide Therapeutics
Phosphorothioates are probably the most popular modifications used in oligonucleotide therapeutics. It involves the substitution of a sulfur atom for a non-bridged oxygen at a phosphate. This modification does not significantly hinder duplex formation, retains the ability of the oligonucleotide duplexes to promote RNase H activity and enhances general nuclease stability. This last property has played key roles in modulating the in vivo half-lives of several approved oligonucleotide therapeutics and many more candidates in earlier clinical stages. This modification also has disadvantages, and the most notable of these is that phosphorothioates, introduced via the standard phosphoramidite method, give additional stereocenters. Each phosphorothioate substitution can be either an “Sp” or “Rp” conformation (Figure 1A). As such, a fully phosphorothioate 20 nt antisense oligonucleotide will be a mixture of more than half a million (219) different molecules. To avoid and/or reduce this type of complexity, one workaround is to use achiral phosphorodithioates instead, where both non-bridged oxygen atoms are replaced with sulfurs. Phosphorodithioates share many of the desirable properties of phosphorothioates without the additional undesired stereocenters.1, 2 In addition, phosphorodithiotes are even more stable to nucleases than their phosphorothioate counterparts. Phosphorodithioates were first developed over thirty years ago. The first oligonucleotide syntheses incorporated dinucleotide phosphoramidites with the phosphorodithioate already in place, and later investigations developed thiophosphoramidites that could be used in place of standard phosphoramidites. One sulfur would come from the thiophosphora.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
