1. Synthesis of a new intercalating nucleic acid 6H-INDOLO[2,3-b] quinoxaline oligonucleotides to improve thermal stability of Hoogsteen-type triplexes
Amany M A Osman, Erik B Pedersen, Jan Bergman Nucleosides Nucleotides Nucleic Acids. 2013;32(2):98-108. doi: 10.1080/15257770.2013.765013.
A new intercalating nucleic acid monomer X was obtained in high yield starting from alkylation of 4-iodophenol with (S)-(+)-2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethanol under Mitsunobu conditions followed by hydrolysis with 80% aqueous acetic acid to give a diol which was coupled under Sonogashira conditions with trimethylsilylacetylene (TMSA) to achieve the TMS protected (S)-4-(4-((trimethylsilyl)ethynyl)phenoxy)butane-1,2-diol. Tetrabutylammonium flouride was used to remove the silyl protecting group to obtain (S)-4-(4-ethynylphenoxy)butane-1,2-diol which was coupled under Sonogashira conditions with 2-(9-bromo-6H-indolo[2,3-b]quinoxalin-6-yl)-N,N-dimethylethanamine to achieve (S)-4-(4-((6-(2-(dimethylamino)ethyl)-6H-indolo[2,3-b]quinoxalin-9-yl)ethynyl)phenoxy)butane-1,2-diol. This compound was tritylated with 4,4'-dimethoxytrityl chloride followed by treatment with 2-cyanoethyltetraisopropylphosphordiamidite in the presence of N,N'-diisopropyl ammonium tetrazolide to afford the corresponding phosphoramidite. This phosphoramidite was used to insert the monomer X into an oligonucleotide which was used for thermal denaturation studies of a corresponding parallel triplex.
2. Regioselective sulfation of β-glucan from Ganoderma lucidum and structure-anticoagulant activity relationship of sulfated derivatives
Zhong Zhang, Qingjiu Tang, Di Wu, Shuai Zhou, Yan Yang, Na Feng, Chuanhong Tang, Jinyan Wang, Mengqiu Yan, Yanfang Liu, Jingsong Zhang Int J Biol Macromol. 2020 Jul 15;155:470-478. doi: 10.1016/j.ijbiomac.2020.03.234. Epub 2020 Mar 30.
In the present study, regioselective sulfation of β-glucan (GLP) from Ganoderma lucidum were firstly established by using 4,4'-dimethoxytrityl chloride and hexamethyldisilazane as protecting precursor. 2,4,6-O-sulfated, 6-O-sulfated and 2,4-O-sulfated GLP derivatives were prepared and the molecular weights (Mw) of derivatives were determined to range from 0.94 × 104 to 6.27 × 104 g/mol, while the degrees of sulfation (DS) were calculated to vary from 0.83 to 1.74. The regioselective sulfation of GLP was confirmed by FT-IR, 13C NMR spectroscopy and methylation analysis. Results indicated that the sulfated substitution sites were predominantly at C-6 in 6-O-sulfated GLP (S6-OGLP) and C-4 in 2,4-O-sulfated GLP (S2,4-OGLP), respectively. Clotting assays (APTT, PT and TT) in vitro showed that sulfate groups were essential for anticoagulant activity and S6-OGLP exhibited much higher than others. Meanwhile, sulfated GLP with higher DS and Mw showed stronger anticoagulant activity in the case of the same condition.
3. A spectrophotometric method for the estimation of amino groups on polymer supports
R K Gaur, K C Gupta Anal Biochem. 1989 Aug 1;180(2):253-8. doi: 10.1016/0003-2697(89)90426-0.
A simple and sensitive method for the estimation of polymer-supported amino groups is reported. The polymer support is treated either with N-succinimidyl-4-O-(4,4'-dimethoxytrityl)-butyrate or 2,4-dinitrophenyl-4-O-(4,4'-dimethoxytrityl)-butyrate and a catalytic amount of 4-dimethylaminopyridine. After removal of the excess reagent through washing, a weighed quantity of the polymer support is treated with perchloric acid to release the 4,4'-dimethoxytrityl cation from the solid support into the solution. The released 4,4'-dimethoxytrityl cation, which has a strong absorption (epsilon 498 = 70,000/M) at 498 nm, is determined spectrophotometrically. A comparative study of these reagents with N-succinimidyl-3-(2-pyridyldithio)-propionate, 4,4'-dimethoxytrityl chloride, and sodium 2,4,6-trinitrobenzenesulfonate methods is also included.
