Fluorous benzyl protective group

Scheme 3.18 Synthesis (box) and use of a fluorous benzyl protective group...

Curran, DP, Feiritto R, Hua Y. Preparation of a fluorous benzyl protecting group and its use in fiuorous synthesis approach to a disaccharide. Tetrahedron Lett. 1998 39 4937 940. 

D. P. Curran, R. Ferritto, Y. Hua, Preparation of a Eluor-ous Benzyl Protecting Group and its Use in a Fluorous Synthesis Approach to a Disaccharide , Tetmzhedron Lett. 1998, 39, 4937. 

The assembly of tetrapeptide 19 that contains all possible 0-dipeptide bonds, (03-03)-, (03-02)-, and (02-03), and also a turn inducing 03-(R)-Ala-02-(R)-Val element was achieved employing a Boc-strategy (Scheme 5). A fluorous benzyl group was incorporated in the first amino acid to streamline the purification procedure by fluorous solid phase extraction (LSPE) (Lilippov et al. 2002 de Visser et al. 2003). Thus, the assembly of the fully protected tetrapeptide commenced with the construction of the first 03-03-peptide bond by applying the previously established conditions. A residence time of 3 min at 90°C provided the Boc-protected dipeptide 15 in 91% isolated yield after LSPE. Notably, the product precipitated in the collection flask, which was kept at ambient temperature, indicating the poor solubility of this class of compounds (Hessel et al. 2005). 

Oligosaccharide syntheses have also been performed in parallel using a fluorous support.A benzyl-type protecting group (HfBn) used in some of these procedures is shown in Figure 7.26. The novel approach here is that the fluorous group or tag is recycled and this can be achieved fairly easily... 

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