No abstract

No abstract

In this report, we describe the design of an efficient and robust sulfurization step in the production process of phosphorothioate (PS) oligonucleotides by solid-phase synthesis. Average stepwise sulfurization efficiencies >99.9% were obtained with “aged” solutions of phenylacetyl disulfide (PADS) in the solvent system acetonitrile/3-picoline (0.2 M, 1:1, v/v). Preparation of the reagent at least 1 day prior to use yields PS-oligonucleotides with low-level phosphate (PO) diester content. The use of freshly prepared PADS solutions gave oligonucleotide products with increased PO-diester content (stepwise sulfurization efficiency 99.5−99.7%). Short aging periods combined with short sulfurization contact times lead to formation of oligonucleotide 4,4‘-dimethoxytrityl-C-phosphonate derivatives. Investigation of reagent stability and sulfurization efficiency revealed significant changes in solution composition over time caused by dissociation of the PADS molecule. The “in situ” formation of a reactive intermediate, presumably a polysulfide, appears to be crucial for optimal synthesis results.

No abstract

The reactions between hydrogen chloride and α-, β-, and γ-butylene have been investigated in both the liquid and gaseous states. The effect of temperature and concentration of the reactants on the reaction velocities was studied and the reaction products were examined. In the liquid state the γ-isomer reacts rapidly, the α- much more slowly and the β- slowest of all. In the gaseous state at atmospheric pressure only γ-butylene shows a measurable reaction which is bimolecular and probably heterogeneous. The liquid reactions were found to be homogeneous. Where possible the freezing-point curves of the systems were determined in order to ascertain the extent of molecular compound formation. The results obtained bear out the conclusions arrived at from previous work on the effect of molecular attraction upon reaction velocity, and indicate the existence of a catalytic factor peculiar to the liquid state. Suggestions as to the mechanism of such a catalysis are offered.