Fluorous-phase label

Hungerhoff B, Sonnenschein H, Theil F (2002) Combining lipase-catalyzed enantiomer-selective acylation with fluorous phase labeling a new method for the resolution of racemic alcohols. J Org Chem 67 1781-1785... 

In conclusion, we have successfully demonstrated that, by using a fluorous label and a fluorous solvent, we can affect the phase transfer of gold and CdSe nanoparticles from an aqueous or hydrocarbon medium to the fluorous phase. Single-walled carbon nanotubes and ZnO nanorods can be solubilized in a fluorous solvent after interaction with a fluorous amine. Phase transfer of the nanostructures to a fluorous solvent represents solubilization in a highly nonpolar solvent, accompanied by purification. The high nonpolarity of the fluorocarbon makes it possible to study the optical and other properties of nanostructures in a medium of very low refractive index. Since the fluorocarbon extracts only the species attached to the fluorous label, the process enables one to obtain solely one product in the pure state. We believe that fluorous chemistry may have practical utility in carrying out studies of nanostructures. 

Fluorous synthesis has certain analogies to solid-phase synthesis the fluorous label and the fluorous phase fulfil functions similar to those of the linker and the solid phase in that both provide a means of removing the attached compound from the reaction mixture (one because of its high affinity to the fluorous phase, the other via a covalent link to the solid support).The similarity, however, also extends to the necessity of additional synthesis steps involved in the attachment to and cleavage from the linker. Otherwise, the fluo-... 

CH2)mRfn and serve a like dissolves like function. When such phase labels are present in sufficient length or quantity, the fluorous phase affinity (fluorophilicity) of the compound can be extremely high. This characteristic is used in the design of dyes that adhere strongly to Teflon. Molecules that have large numbers of such fluorine atoms - typically from 39 to > 100 - are called heavy fluorous compounds. However, for certain applications moderate fluorous phase affinities suffice, and for the compounds used in such applications, the term light fluorous is sometimes utilized (Table 3.1). 

Fluorous chemistry, involving the use of a fluorous label for the functionalization of a substrate and a fluorous solvent for extraction of the functionalized substrate, is shown to be effective in solubilizing gold and CdSe nanoparticles in a fluorous medium, through phase transfer from an aqueous or a hydrocarbon medium. While these nanoparticles were functionalized with a fluorous thiol, single-walled carbon nanotubes and ZnO nanorods could be solubilized in a fluorous medium by reacting them with a fluorous amine. Fluorous chemistry enables the solubilization of the nanostructures in the most nonpolar liquid medium possible. 

A somewhat different approach was used by Vincent in phase-switching reactions using pyridyl-labelled substrates and products. The pyridyl-containing tag is here thought of as a masked phase tag, which allows for phase switching with the help of a heavy fluorous copper(ll)-carboxylate complex. Comparison with a non-fluorous system indicated that a problem of release of the strongly coordinating pyridine linker was avoided in the fluorous approach. ... 

Fluorous reverse phase silica gel (FRPSG) has been used in the purification of synthetic DNA fragments.In solid phase DNA synthesis, truncated sequences are often separated from the desired product after deprotection using HPLC or electrophoresis. In order to perform, parallel syntheses and separations of nucleotides the trityl-on purification procedure was developed, in which a lipophilic support material is used to separate the desired and undesired product, followed by deprotection. If the protecting group is labelled with a fluorous group, fiuorous-fiuorous interactions between the FRPSG and the protected nucleotide can be used to aid separation of the aqueous mixture. 

Recently, fluorous chemistry has been used to solubilize and phase-transfer nanocrystals of metals (Au) and chalcogenides (CdS) as well as inorganic nanorods (ZnO) [551]. Here, a fluorous label (e.g. fluorinated alkane thiol) is attached to the nanostructures which are then readily extracted by a fluorocarbon from aquous or hydrocarbon solutions, due to fluorine-fluorine interaction. This method not only enables the purification of the nanostructures, but also helps one to study them in the most-nonpolar medium possible, the refractive index of fluorocarbon being around 1.2. 

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