FMOC chloride

Starting from L-tryptophan, immobilized on hydroxyethyl polystyrene through its carboxylic group, the intermediate a,[3-unsaturated imine (554) was formed by reaction with 3-methylcrotonaldehyde in pure trimethyl orthoformate (TMOF). The imine was then allowed to react with Fmoc chloride in the presence of pyridine to afford the required tetrahydro-[3-carboline (555) through an N-acylimin-ium ion mediated Pictet-Spengler-type cyclization. Further manipulation of the Pictet-Spengler product afforded the desired demethoxy-FTC as the minor cis isomer, along with its C-3 trans epimer (556) (diastereoisomeric ratio 1 3) (Scheme 115). 

Both primary and secondary ammo acids react with 9-fluorenylmethyl chloroformate (FMOC chlonde) under alkaline, aqueous conditions (Anson-Moye and Boning, 1979). The reaction is complete in 30 s. However, although FMOC chloride is fluorescent, the excess reagent and the byproducts are easily removed by extraction prior to separation (Ejnarsson et al., 1983). 

Mass spectrometry is certainly required for correct identification of an unknown peak (Larson, 1982). Less complicated ways may, however, be employed to test the homogeneity of a peak (1) Elution with different gradient systems and at different pHs can also be used. (2) Quantification should be similar with different derivatives, e.g., those formed with OPA and FMOC chloride (Ejnarsson et al., 1983), and with different principles of chromatography, i.e. reversed-phase and ion-exchange (3) An attractive method was recently described by Joseph and Davies (1983), with fluorimetric and electrochemical detection in series, confirmation of the identities of the OPA derivatives was obtained in a single run. 

The instability and chemical conversion of some OPA derivatives imply that a denvatized compound may, in fact, result in one fluorescent and two radioactive peaks (Simson and Johnson, 1976, Fig. 1). The chemical rearrangement of the derivatives may, however, be a minor factor with respect to retention and the fluorescent and nonfluorescent derivatives may coelute. The use of more chemically stable amino acid derivatives, i.e. those formed by reaction with FMOC chloride, eliminates this problem. When the radioactivity of an amino acid is measured, it is often desirable and necessary to inject larger concentrations of amino acids than in a routine expenment. With the OPA method it is then critical to (a) make sure that OPA is present in the required molar excess (Lindroth and Mopper, 1979), (b) lower the pH of the reagent mixture to spare the top of the column, and (c) use the same or lower proportion of organic solvent in the sample as in the beginning of the gradient in order to obtain a concentration of the derivatives on the column top. 

Derivatized Species By exploring the specific reactivity of the primary amine group, derivative methods including with Fmoc chloride and 4-(dimethylamino)benzoic acid have been developed to enhance the analysis of PE species [44—46]. The enhancement of ionization efficiency in the negative-ion mode is achieved after derivatization through turning weakly anionic lipids (or weakly zwitterionic lipids) into anionic lipids (Chapters 2 and 3). 

Fmoc-N3, NaHC03, aq. dioxane, 88-98% yield.This reagent reacts more slowly with amino acids than does the acid chloride. It is not the most safe method for Fmoc introduction because of the azide. 

This method is suitable for the preparation of BOC, Fmoc, Adoc, and Bpoc protected amino acids. The acid chloride is a stable, storable solid. ... 

This tertiary ester was developed to reduce aspartimide and piperidide formation during the Fmoc-based peptide synthesis by increasing the steric bulk around the carboxyl carbon. A twofold improvement was achieved over the the standard Fbutyl ester. The Mpe ester is prepared from the acid chloride and the alcohol and can be cleaved under conditions similar to those used for the r-butyl ester. ... 

A derivatization with acid chlorides is also possible. Amino acids can be derivatized with 9-fluorenylmethyl chloroformate (FMOC) and separated on a CSP with X-cyclodextrin (ChiraDex gamma ), a cyclic oligosaccharide which consists of eight glucose units. 

To a 50-mL polypropylene vial (Note 1) are added 0.839 g (2.67 mmol) of 2-[ethyl[4-[(lE)-(4-nitrophenyl)azo]phenyl]amino]ethanol (Disperse Red 1, Note 2), 0.985 g of (2.39 mmol) N-[(9H-fluoren-9-ylmethoxy)carbonyl]-L-aspartic acid,l-(l, 1-dimethylethyl) ester (Fmoc-L-Asp-OtBu, Note 3), 3.26 g (4.73 mmol) of polystyrylsulfonyl chloride resin (Note 4), and 30 mL anhydrous methylene chloride (Note 5). The vial is capped and the mixture is shaken for five min (Note 6). N-Methylimidazole (0.764 mL, 9.58 mmol) is then added to the deep red mixture (Note 7) and the resulting mixture is shaken for 2 hr (Note 8). 

Fig. 7 Kinetics of microwave-assisted loading of 2-chlorotrityl chloride resin with Fmoc-isoleucine at 110 °C. For comparison, the dashed line indicates the level of loading after 1 h at room temperature...

Investigation of the microwave-assisted attachment of Fmoc-protected amino acids onto 2-chlorotrityl chloride resin indicated higher loadings and increased rates compared to standard room temperature procedures [146]. In this comparative study standard procedures yielded 0.37 mmol/g loading after 1 hour, whereas at 110 °C using microwave dielectric heating, a similar result (0.38 mmol/g) was obtained after only 15 min (Fig. 7). 

Hydroxamic acids are an important class of compounds targeted as potential therapeutic agents. A-Fmoc-aminooxy-2-chlorotrityl polystyrene resin 61 allowed the synthesis and subsequent cleavage under mild conditions of both peptidyl and small molecule hydroxamic acids (Fig. 14) [70]. An alternative hydroxylamine linkage 62 was prepared from trityl chloride resin and tV-hydroxyphthalimide followed by treatment with hydrazine at room temperature (Scheme 30) [71]. A series of hydroxamic acids were prepared by the addition of substituted succinic anhydrides to the resin followed by coupling with a variety of amines, and cleavage with HCOOH-THF(l 3). 

Dimethylformamide (DMF), dioxane, piperidine, methylene chloride, acetonitrile, trimethyl orthoformate (TMOF), sodium borohydride, diisopropylcarbodiimide, and trifluoroacetic acid (TFA) were purchased from Aldrich Chemical Company, Inc. and used without further purification. All of the diversity reagents were purchased from Aldrich except for Fmoc-glycine-OH, which was purchased from Novabiochem. 

Kenne and associates (57) have applied this procedure for the synthesis of a-D-mannopyranosyl derivatives linked to L-serine/L-threonine (59 and 60). Compounds 59 and 60 were obtained by coupling 2,3,4,6-tetra-<9-acetyl-D-mannopyranosyl chloride (56) with Fmoc-L-serine benzyl ester or Fmoc-L-threonine benzyl ester in the presence of silver triflate and 4-A molecular sieves, followed by deprotection (57). 

Two other reagents used in HPLC are 9-fluorenyl methoxycarbonyl chloride (FMOC) and phenylisothiocyanate (PITC). 9-fluorenyl methoxycarbonyl chloride is becoming increasingly popular in protein chemistry research because it reacts with secondary amines and also offers rapid analysis of protein hydrolysates. 

FIGURE 2.14 Peptide-bond formation from chlorides of A-alkoxycarbonylamino acids. N-9-Fluorenylmethoxycarbonylamino-acid chlorides.41 The base is NaHCO, Na2C03, or a tertiary amine. The reaction is carried out in a one- or two-phase system. The latter is used to try to suppress formation of the 2-alkoxy-5(4//)-oxazolone that is generated by the action of the base on the acid chloride. The method is applicable primarily to Fmoc-amino-acid derivatives that do not have acid-sensitive protecting groups on their side chains. 

S Pass, B Amit, A Parchomik. Racemization-free photochemical coupling of peptide segments. (Fmoc-amino-acid chlorides) J Am Chem Soc 103, 7674, 1981. 

LA Carpino, BJ Cohen, KE Stephens, SY Sadat-Aalaee, J-H Tien, DC Lakgridge. (9-Fluorenylmethyl)oxycarbonyl (Fmoc) amino acid chlorides. Synthesis, characterization, and application to the rapid synthesis of short peptide segments. J Org Chem 51, 3732, 1986... 

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