Accurate molecular weight measurements of nucleoside phosphoramidites: a suitable matrix of mass spectrometry

Development of New Synthetic Reactions Using Hetero-Heavy Atoms and Their Application to Synthesis of Biofunctional Molecules

Novel reactions using hetero-heavy atoms (P, S, Si, Se, and Sn) were developed and applied to the synthesis of biofunctional molecules and some medicine-candidates, in which the following items are covered. 1) Development of introduction of C₁-unit using cyanophosphates (CPs). 2) Carbene-generation under neutral condition from CPs and its application to organic synthesis. 3) [3,3]Sigmatropic rearrangement-ring expansion reactions of medium-sized cyclic thionocarbonates containing a sulfur atom and their application to natural product synthesis. 4) Stereoselective synthesis of novel β-imidazole C-nucleosides via diazafulvene intermediates and their application to investigating ribozyme reaction mechanism. 5) Developments of novel histamine H₃- and H₄-receptor ligands using new synthetic methods involving Se or Sn atoms.

Transformation of Carbonyl Compounds into Homologous Alkynes under Neutral Conditions: Fragmentation of Tetrazoles Derived from Cyanophosphates

Cyanophosphates (CPs) can be easily prepared from either ketones or aldehydes, and their reaction with NaN₃-Et₃N·HCl results in the formation of azidotetrazoles. Under microwave irradiation, successive fragmentation of the azidotetrazoles generates alkylidene carbenes that undergo [1,2]-rearrangement and are transformed into homologous alkynes. Treatment of ketone-derived CPs with TMSN₃ and Bu₂SnO as catalyst in toluene at reflux directly yields the corresponding internal alkynes, whereas the reaction of aldehyde-derived CPs with NaN₃-Et₃N·HCl in THF at reflux or TMSN₃-Bu₂SnO (cat.) in toluene at reflux provides homologous terminal alkynes in good yields. These reactions take place under neutral conditions and can be successfully extended to obtain alkynes that are not usually accessible from the corresponding carbonyl compounds by the Ohira-Bestmann or Shioiri procedures, which require basic conditions.

An electrospray mass spectrometric method for accurate mass determination of highly acid-sensitive phosphoramidites

An accurate mass determination method utilizing electrospray ionization mass spectrometry is described for analysis of several different types of phosphoramidites that are extremely acid-sensitive compounds. An earlier method, which applied a LiCl/acetonitrile system, was extended for this special application by using polymeric standards including poly(ethylene glycol) (PEG), poly(ethylene glycol) dimethyl ether (PDE) and poly(propylene glycol) (PPG). Concentrations of standards, samples and LiCl were optimized and potential impurities that affect the analyses were also investigated.

Mass determination of phosphoramidites

Nucleoside phosphoramidites are the most widely used building blocks in contemporary solid-phase synthesis of oligonucleotides. The accurate molecular weight measurements of such molecules, which are acid-labile compounds, may be easily determined by mass spectrometry using a matrix system, triethanolamine/NaCl, on a liquid secondary ion mass spectrometer (LSIMS) or fast-atom bombardment (FAB) MS equipped with a double-focusing mass spectrometer. The present method rapidly and easily measures the accurate molecular weights of various phosphoramidites as adduct ions [M+Na]+ with an average mass error smaller than 0.4 ppm, allowing determination of the formulas of the phosphoramidites in place of elemental analysis. Further, it was found that intensities of molecular-related ions could be enhanced to the highest degree by adjustment of the molar ratio of phosphoramidite and NaCl, fixing the amount of triethanolamine on LSIMS, making the present method a powerful tool for identification of phosphoramidites by mass spectrometry.