1. Oligoribonucleotides with 2'-O-(tert-butyldimethylsilyl) groups
L Bellon Curr Protoc Nucleic Acid Chem. 2001 May;Chapter 3:Unit 3.6. doi: 10.1002/0471142700.nc0306s01.
The chemical synthesis of oligoribonucleotides on solid support is routinely performed via the phosphoramidite method. However, the additional 2-OH function of the ribofuranosyl sugar requires suitable protection during oligoribonucleotide synthesis. This unit describes methods for 2-OH protection using the TBDMS group.
2. Simple Tyrosine Derivatives Act as Low Molecular Weight Organogelators
Güzide Aykent, Cansu Zeytun, Antoine Marion, Salih Özçubukçu Sci Rep. 2019 Mar 20;9(1):4893. doi: 10.1038/s41598-019-41142-z.
The gelation of L-Tyr(tBu)-OH in tetrahydrofuran (THF) was discovered serendipitously. It was noted that this tremendously low molecular weight (LMW) compound has the ability to gel a wide variety of organic solvents (e.g., N,N-Dimetylformamide (DMF), THF, butanol, toluene), even in very low concentrations (i.e., 0.1 wt/v% in DMF). Addition of bases such as NaOH and piperidine enhanced the gel property. By changing the side-chain protecting group to tert-butyldimethylsilyl (TBDMS), a fluoride ion-responsive organogel was also acquired. This new organogelator responded fluoride ion concentration as low as 0.2 ppm. Characterization of microstructures and gel behaviours were studied by powder X-Ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), rheological measurements and molecular dynamics (MD) simulations. Experimental observations and theoretical simulations consistently show a fibre-like structure of the gel, in which the organogelator molecules are held together via a dense network of hydrogen bonds, and via van der Waals interactions between hydrophobic groups.
3. Synthesis of chiral 1,4-oxazepane-5-carboxylic acids from polymer-supported homoserine
Petra Králová, Barbora Lemrová, Michal Maloň, Miroslav Soural RSC Adv. 2020 Sep 30;10(59):35906-35916. doi: 10.1039/d0ra07997a. eCollection 2020 Sep 28.
The preparation of novel 1,4-oxazepane-5-carboxylic acids bearing two stereocenters is reported in this article. Fmoc-HSe(TBDMS)-OH immobilized on Wang resin was reacted with different nitrobenzenesulfonyl chlorides and alkylated with 2-bromoacetophenones to yield N-phenacyl nitrobenzenesulfonamides. Their cleavage from the polymer support using trifluoroacetic acid (TFA) led to the removal of the silyl protective group followed by spontaneous lactonization. In contrast, TFA/triethylsilane (Et3SiH)-mediated cleavage yielded 1,4-oxazepane derivatives as a mixture of inseparable diastereomers. The regioselectivity/stereoselectivity depended on the substitution of the starting 2-bromoacetophenones and was studied in detail. Catalytic hydrogenation of the nitro group improved the separability of the resulting diastereomeric anilines, which allowed us to isolate and fully characterize the major isomers.
