Fluorous HPLC separation

Figure 7.2 Fluorous HPLC separation of a fluorous mixed synthesis reaction mixture.

Figure 7.3 Fluorous HPLC separation of fluorinated dendrimers. (a) Structure of fluori-nated dendrimers C0-C3 and (b) HPLC profile of fluorinated dendrimers on fluorous, normal phase, and reverse phase.

A significant amount of effort in fluorous analytical chemistry is directed towards fluorous HPLC and new fluorous silicas for the separation of fluorous molecules. However, it should be noted that fluorous molecules sometimes interact sufficiently with conventional silicas that standard chromatographic... 

Glatz, H., Blay, C., Engelhardt, H. and Bannwarth, W. (2004) New fluorous reversed phase silica gel for HPLC separations of perfluorinated compounds. Chromatographia, 59, 567-570. 

It is also possible to perform flash chromatographic and HPLC separations with fluorous silica gel. The HPLC separations are the cornerstone of the new technique of... 

On reaching the stage of fluorous separation, three methods are usually used for the rapid separation of fluorous compounds from the reaction mixture fluorous hquid-phase extraction, fluorous solid-phase extraction [6], and fluorous HPLC [7]. 

Third, fluorous HPLC is able to separate fluorous compounds from each other by decoding the fluorine content diflerences between fluorous compounds. The difference between FSG-based sohd-phase extraction and chromatography lies in the loading level of the samples. At a low loading level, the resolution of fluorous components increases and, therefore, multiple fractions with different fluorine contents can be collected as different components that is, fluorinated components... 

It is noteworthy that the fluorine content differences can be generated by attaching either similar reaction domains to different fluorous tags [13] or the same fluorous tag to reaction domains of different sizes (Figure 7.1). For example, a class of fluorinated dendrimers with the same fluorinated domain (fluorous tag), G0-G3, can be separated from each other by fluorous HPLC because of the over 10% differences in their fluorine content (Figure 7.3). Comparing the HPLC profile of dendrimers on the fluorous phase with that on normal phase and reverse phase, it is clear that fluorous HPLC gives the best separation. 

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. 

Separate the mixtures (demixing) of tagged products by high-performance chromatography (HPLC) on a fluorous stationary phase (F-HPLC). 

Enantiopure or enantioenriched compounds can be obtained by asymmetric synthesis or by separation of a racemic reaction mixture. Quasi-racemic FMS provides a new approach to enantiomeric compounds (see Scheme 13.2) [26, 27]. Quasi-racemic synthesis starts with two individual R- and 5-enantiomers attached to two different fluorous tags. After steps of mixture synthesis followed by F-HPLC demixing and detagging, two individual products as enantiomers are obtained (see Sections 13.2.1 and 13.2.2). The separation and identification of the final quasi-enantiomers are ensured by the phase-tag-based F-HPLC. In a more complicated quasi-racemic FMS, additional enantiomerically pure building blocks and fluorous tags can be used to generate more chiral centers and more than two products as stereoisomers (see Sections 13.2.3 to 13.2.8). 

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