Preparation of tert-butoxycarbonyl derivatives of amino acids using di-tert-butyl pyrocarbonate

In order to optimize and individualize the process, the influence of conditions of the reactions on the synthesis of Boc derivatives of amino acids using di-tert-butyl pyrocarbonate on the yield of desired product has been studied.     

Preparation of tert-butoxycarbonyl derivatives of amino acids using di-tert-butyl pyrocarbonate

In order to optimize and individualize the process, the influence of conditions of the reactions on the synthesis of Boc derivatives of amino acids using di-tert-butyl pyrocarbonate on the yield of desired product has been studied.Institute of Biological and Medical Chemistry, Academy of Medical Sciences of the USSR, Moscow. NPO Biokhimreaktiv All-Union Scientific-Research Institute of Applied Biochemistry, Olaine. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 543–548, July–August, 1979.     

Trace analysis of residual methyl methanesulfonate, ethyl methanesulfonate and isopropyl methanesulfonate in pharmaceuticals by capillary gas chromatography with flame ionization detection

A capillary gas chromatographic method using flame ionization detection was developed and validated for the trace analysis (ppm level) of methyl methanesulfonate, ethyl methanesulfonate, and isopropyl methanesulfonate in pharmaceutical drug substance. The method utilizes a megabore capillary column with bonded and crosslinked polyethylene glycol stationary phase. A dissolve-and-injection approach was adopted for sample introduction in a splitless mode. The investigated sample solvents include acetonitrile, ethyl acetate, methylene chloride, 1,2-dichloromethane, and toluene. Aqueous mixtures of acetonitrile and water can also be used as sample solvent. A limit of detection of about 1 microg/g (1 ppm) and limit of quantitation of 5 microg/g (5 ppm) were achieved for the mesylate esters in drug substance samples. The method optimization and validation are also discussed in this paper.     

Use of di-tert-butyl pyrocarbonate to obtain N-tert-butoxycarbonyl derivatives of amino acids

Summary It has been shown that BOC derivatives of amino acids can be obtained by the tert-butoxycarbonylation of amino-acid salts with di-tert-butylpyrocarbonate in aqueous organic solutions.Institute of Biological and Medicinal Chemistry, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 764–767, November–December, 1974.     

Cationic liposomes and nucleic acids

During the past decade, cationic lipids have emerged as the primary choice for gene delivery in vitro, i.e. transfection of cultured cells. A number of lipids with cationic head groups have been synthesized and evaluated. However, their success in vivo for gene therapy has been limited. To date, simple electrostatic complexes of cationic lipid mixtures with DNA have been hampered in numerous aspects: lack of colloidal stability, relatively low efficiency observed as expression levels or % of transfected cells, short duration of expression, and most importantly, non-specific interactions with many cells and tissues. Appreciation of the complexity of in vivo requirements, and especially opposing requirements for extra- and intracellular trafficking, is leading to engineered designs of gene delivery vectors containing cationic lipids. These designs attempt to assemble layered colloidal systems that accommodate the multiple functions required to traverse the various extra- and intracellular barriers. Successful development of such systems will depend on the ability to characterize and optimize each step rather than rely only on reporter gene expression, in addition to the obvious need to characterize the layered nature of the complexes. Importantly, many pharmacological aspects must be considered, especially control of the biodistribution and toxicity. Initial reports on such systems appear to provide at least a proof of the concept.     

Adsorption of nucleic acids on collodion films

Adsorption of nucleic acids on collodion films from solutions of different ionic strengths was studied, and the adsorption equilibrium constants were determined. The primary adsorption of DNA samples on collodion films was examined depending on various factors. A comparative analysis of different techniques (vacuum drying, UV irradiation) employed for immobilization of DNA samples on collodion films was carried out.     

Voltammetric study of the interaction of ciprofloxacin-copper with nucleic acids and the determination of nucleic acids

The behavior of the ciprofloxacin (CPFX) complex with copper, Cu(II)L₂, at a mercury electrode has been investigated in borax–boric acid buffer. The adsorption phenomena were observed by linear sweep voltammetry. The mechanism of the electrode reaction was found to be reduction of Cu(II)L₂ adsorbed on the surface of the electrode by an irreversible charge transfer to metal amalgam, Cu(0)(Hg). In the presence of DNA, the formation of the electrochemically non-active complexes Cu(II)L₂–DNA results in the decrease of the equilibrium concentration of Cu(II)L₂ and its peak current. Under the optimum conditions, the decrease of the peak current is proportional to DNA concentration. The linear ranges are 6.67×10⁻⁸ to 1.20×10⁻⁵ g ml⁻¹ for calf thymus DNA (ctDNA), 3.30×10⁻⁸ to 2.33×10⁻⁶ g ml⁻¹ for fish sperm DNA (fsDNA) and 1.0×10⁻⁸ to 1.2×10⁻⁶ g ml⁻¹ for yeast RNA. The detection limits are 5.00×10⁻⁹, 3.00×10⁻⁹ and 2.50×10⁻⁹ g ml⁻¹, respectively. This method exhibits good recovery and high sensitivity.     

Pulse-polarographic analysis of nucleic acids and proteins

Nucleic acids and proteins were studied by means of derivative and normal pulse polarography, and d.c. and a.c. polarography in connection with the dropping mercury electrode. It was shown that natural ribonucleic acids, as transfer, ribosomal and viral RNAs yield derivative pulse-polarographic peaks; from their heights and potentials conclusions can be made about their content of ordered structure in solution, similarly as in the case of deoxyribonucleic acids studied earlier. Synthetic single-stranded polyribo-cytidylic acid yields a well developed peak, whereas in the double-helical complex with polyriboguanylie acid it is inactive when using either derivative pulse polarography or d.c. polarography. Well developed peaks were obtained also with albumin (a protein containing reducible?S?S? groups), while only an inflex was observed on the d.c. polarogram. Proteins were also studied in media containing cobalt (Brdi?ka's solution) or nickel and it was shown that derivative pulse polarography due to its high sensitivity and accuracy enables us to carry out the measurements even in less common media than Brdi?ka's solution. This fact could be exploited in clinical chemistry as well as in the investigation of the nature of catalytic currents of proteins. The currents of double-helical polynucleotides obtained by means of normal pulse polarography exhibit a marked dependence on the initial potential and cannot represent a reliable indicator of structural changes of biopolymers in solution. They can however, be used in studies of the influence of the polynucleotide adsorption at different potentials on the subsequent reduction.     

Alkylation of nucleic acids and their components

In water at pH 5–6,-(N--chloroethyl-N-methylamino)propylphthalimide (I) alkylates guanosine to give 7-{-[N-methyl-N-(-phthalylimidopropyl)amino]ethyl} guanosine. The latter is converted to 7-{-[N-methyl-N-(-phthalylimidopropyl)amino] ethyl} guanine and 7-[-(N--aminopropyl-N-methylamino) ethyl]guanine. At pH 9, I and its derivatives undergo opening of the phthalimide ring to give o-carboxybenzamido derivatives. The chief transformation of I at pH 6 is self-alkylation to give quaternary ammonium bases. The pK _a and true rate constant for ionization of the chlorine of the-chloroethylamino group were determined for I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 413–418, March, 1973.See [1] for communication VI.     

Alkylation of nucleic acids and their components

Guanosine, cytidine, inosine, and thymine react with 4-[N-(-chloroethyl)-N-methylamino]-benzaldehyde to give 7-alkylguanosine, 3-alkylcytidine, 1-alkylinosine, and 1-alkylthymine, respectively. The order of reactivities of the nucleosides with respect to 4-[N-(-chloroethyl)-N-methylamino] benzaldehyde in 36% aqueous dioxane at 50°C and pH 5–6 is guanosine > inosine > cytidine > thymine. Inosine, cytidine, and thymine are 36%, 21%, and 13% as reactive as guanosine. Adenosine and uridine do not react under these conditions. The ratio of the rate constant for the alkylation of guanosine by 4-[N-(-chloroethyl)-N-methylamine]-benzaldehyde and the rate constant for the hydrolysis of the latter in 17% aqueous dioxane at 50° and pH 5–6 is 10.5±0.5 mole^–1. The alkylation of guanosine at pH 7.5 is accompanied by cleavage of the imidazole ring of the 7-alkylguanosine, which proceeds at a higher rate than the rate of the limiting step — ionization of 4-[N-(-chloroethyl)-N-methylamino]benzaldehyde. The transformations of the alkylated nucleosides in acids and alkalis were studied, and the rate constants of these transformations were determined.See [26] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 109–116, January, 1972The authors thank D. G. Knorre for discussing the kinetic results of this research.