1. Novel fluorogenic probe for fluoride ion based on the fluoride-induced cleavage of tert-butyldimethylsilyl ether
Xiao-Feng Yang Spectrochim Acta A Mol Biomol Spectrosc. 2007 Jun;67(2):321-6. doi: 10.1016/j.saa.2006.07.020. Epub 2006 Jul 15.
A highly sensitive and selective fluorogenic probe for fluoride ion, 4-methylumbelliferyl tert-butyldimethylsilyl ether (4-MUTBS), was designed and synthesized. 4-MUTBS was a weakly fluorescent compound and was synthesized via the one-step reaction of 4-MU with tert-butyldimethylsilyl chloride. Upon incubation with fluoride ion in acetone-water solution (7:3, v/v), the Si-O bond of 4-MUTBS was cleaved and highly fluorescent 4-methylumbelliferone (4-MU) was released, hence leading to the fluorescence increase of the reaction solution. The fluorescence increase is linearly with fluoride concentration in the range 50-8000 nmol l(-1) with a detection limit of 19 nmol l(-1) (3sigma). Because of the high affinity of silicon toward fluoride ion, the proposed probe shows excellent selectivity toward fluoride ion over other anions. The method has been successfully applied to the fluoride determination in toothpaste and tap water samples.
2. Preparation of 6(1),6n-di-O-(tert-butyldimethylsilyl)-cyclomalto-octaoses
T Tanimoto, T Sakaki, T Iwanaga, K Koizumi Chem Pharm Bull (Tokyo). 1994 Feb;42(2):385-7. doi: 10.1248/cpb.42.385.
Four positional isomers of 6(1),6n-di-O-(tert-butyldimethylsilyl)- cyclomalto-octaose (n = 2-5) were prepared by reaction of cyclomalto-octaose (1, cG8) with tert-butyldimethylsilyl chloride in pyridine, and were isolated by high-performance liquid chromatography. The regiochemical determination of those positional isomers was performed by comparison with authentic compounds, prepared from 6(1),6n-di-O-trityl-cG8s (n = 2-5).
3. Facile synthesis of per(6-O-tert-butyldimethylsilyl)-α-, β-, and γ-cyclodextrin as protected intermediates for the functionalization of the secondary face of the macrocycles
Gábor Benkovics, Milo Malanga, Giovanna Cutrone, Szabolcs Béni, Antonio Vargas-Berenguel, Juan Manuel Casas-Solvas Nat Protoc. 2021 Feb;16(2):965-987. doi: 10.1038/s41596-020-00443-8. Epub 2021 Jan 15.
Per(6-O-tert-butyldimethylsilyl)-α-, β- and γ-cyclodextrin derivatives are well-known as synthetic intermediates that enable the selective mono-, partial, or perfunctionalization of the secondary face of the macrocycles. Although silylation of the primary rim is readily achieved by treatment with tert-butyldimethylsilyl chloride in the presence of pyridine (either alone or mixed with a co-solvent), the reaction typically results in a mixture containing both under- and oversilylated byproducts that are difficult to remove. To address this challenge in preparing a pure product in high yield, we describe an approach that centers on the addition of a controlled excess of silylating agent to avoid the presence of undersilylated species, followed by the removal of oversilylated species by column chromatography elution with carefully designed solvent mixtures. This methodology works well for 6-, 7-, and 8-member rings (α-, β-, and γ-cyclodextrins, respectively) and has enabled us to repeatedly prepare up to ⁓35 g of ≥98% pure product (as determined by HPLC) in 3 d. We also provide procedures for lower-scale reactions, as well as an example of how the β-cyclodextrin derivative can be used for functionalization of the secondary face of the molecule.
