Fmoc, 9-fluorenylmethoxycarbonyl

In SPPS, there are two main protecting groups commonly used for Ai -protection [3] ferf-butoxycarbonyl (Boc) [7] and 9-fluorenylmethoxycarbonyl (Fmoc) [8] (Fig. 2). 

On the other hand, optionally added co-ions of the eluent may also interfere with the ion-exchange process through competitive ion-pairing equilibria in the mobile phase. The effect of various amines added as co-ions to the polar-organic mobile phase was systematically studied by Xiong et al. [47]. While retention factors of 9-fluorenylmethoxycarbonyl (FMOC)-amino acids were indeed affected by the type of co-ion, enantioselectivities a and resolution values Rs remained nearly constant. For example, retention factors k for FMOC-Met decreased from 17.4 to 9.8 in the order... 

For a,a-dialkylamino acids enantiomerization is not a problem. The preparation of 4,4-dimethyl-2-[(9-fluorenylmethyl)oxy]-5(4F/)-oxazolone, an intermediate used in the synthesis of ( )-mirabazole C has been described. Recently, two new 2-aIkoxy-5(4F/)-oxazolones derived from Toac (2,2,6,6-tetramethyl-4-amino-l-oxy-piperidine-4-carboxylic acid) that incorporate Z or 9-fluorenylmethoxycarbonyl (Fmoc) protection at C-2 have been described. The Toac analogues were synthesized as part of a study of the crystal structure and ab initio calculations for these interesting systems. 

In the synthesis of analogues of calicheamicin 71 and esperamicin Ajb, Moutel and Prandi employed the glycosyla-tion of a nitrone with a trichloroacetimidate as a key step - /3-N-O glycosidic bond formation. Preparation of the nitrone begins with the alkylation of the known alcohol 69 <1992CC1494> with 1,4-dibromobutane in the presence of sodium hydride. Subsequent aminoalkylation, amine protection with 9-fluorenylmethoxycarbonyl (Fmoc), and reduction with NaBHsCN were followed by nitrone 70 formation with 4-methoxybenzaldehyde (Scheme 8) <2001J(P1)305>. 

Reactions (T) through are necessary for the formation of each peptide bond. The 9-fluorenylmethoxycarbonyl (Fmoc) group (shaded blue) prevents unwanted reactions at the o-amino group of the residue (shaded red). Chemical synthesis proceeds from the carboxyl terminus to the amino terminus, the reverse of the direction of protein synthesis in vivo (Chapter 27). 

For the 9-fluorenylmethoxycarbonyl (Fmoc) protection of amino acids, Chinchilla et al.36,37 prepared a similar ROMP-polymer that supports an activated. V-hydroxysuccinimide Fmoc-carbonate (Table VII, entry 31). Various Fmoc-amino acids are prepared in pure form after removal of the polymer reagent by filtration and aqueous phase separation. 

In this chapter we will summarize chemical methods for the stereoselective attachment of carbohydrates to amino acids, with particular emphasis on the preparation of building blocks for use in solid-phase glycopeptide synthesis based on the 9-fluorenylmethoxycarbonyl (Fmoc) protective group strategy. 

Fluorenylmethoxycarbonyl (Fmoc) derivatives of amino acids (obtained from Auspep, Australia or Merck, Germany). 

Other research has focused on the interaction of cells with peptide structures that assemble via aromatic interactions. Cells have been grown on the surface of gels formed by Fluorenylmethoxycarbonyl (FMOC) modified diphenylalanine nanotubes (Mahler et al., 2006). Although cells were only grown for short time frames (24 h), the cells were viable on these scaffolds. 

Alsina, J., Yokum, T. S., Albericio, F., and Barany, G. (1999) Backbone amide linker (BAL) strategy for iV -9-fluorenylmethoxycarbonyl (Fmoc) solid-phase syn-... 

All commercial peptide synthesizers are designed to utilize the tert-butoxycarbonyl (Boc)/benzyl (Bzl) and/or the 9-fluorenylmethoxycarbonyl (Fmoc)/tert-butyl (tBu) protection group strategies. Synthesizers originally planned to automate the Boc approach may be readily adapted to perform Fmoc chemistry because the latter incorporates milder reagents. However, this is not the case for instruments suitable for Fmoc-based methods. Valves and tubing on these instruments typically are not compatible with trifluoroacetic acid (TFA), a corrosive reagent that with extended use may destroy proper mechanical operation. 

A major progress in glycopeptide synthesis was achieved when it was demonstrated that the NHj-terminal 9-fluorenylmethoxycarbonyl (Fmoc) group can be selectively removed from glycopeptides using the weak base morpholine (pK 8.3). This holds true for 0-glycosyl serine and threonine esters, which are sensitive to base-catalyzed -elimination of the carbohydrate [10]. 

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