9-Fluorenylmethyl carbonate

Acetate, chloroacetate, benzoate, p-methoxy benzoate, benzyl carbonate (Cbz), tert-butyl carbonate (Boc) and 9-(fluorenylmethyl) carbonate (Fmoc) are commonly prepared to protect the hydroxyl group (Table 1.3). 

Byeon et al. [23] described a fluorimetric method for (z>)-penicillamine using 9-fluorenylmethyl pentafluorophenyl carbonate and acetonitrile. Capsules containing penicillamine were extracted with water and then filtered. The solution was incubated at 70 °C for 40 min with borate buffer solution. After cooling, the mixture was extracted with diethyl ether and the fluorescence of the aqueous phase measured at (excitation = 260 nm, emission = 313 nm). The calibration graph was linear for 0.4-5.0 pM of penicillamine with a coefficient of variation of 0.4%. 

DBU = l,8-diazabicyclo[5.4.0]undec-7-ene (15) is a nonnucleophilic base employed in conjunction with piperidine in dimethylformamide (1 1 48) for removal of fluorenylmethyl-based protectors. The piperidine is necessary as a nucleophile to trap the expelled moiety that does not react with DBU. DBU has no effect on phthalimido [Pth-NH of -Lys(Pht)-], dialky-lphosphoryl [-Tyr(P03R2)-], or Dde-NH [-Lys(Dde)- see Section 6.4], but it promotes aspartimide formation at the pertinent residues of susceptible sequences (see Section 6.13). In dichloromethane, it promotes a reaction between two molecules of urethane-protected amino acid /V-carboxyanhy-dride with release of carbon dioxide (see Section 7.14). 

S. Chalais, A. Cornelis, P. Laszlo, and A. Mathy, Tetrahedron Letters, 26, 2327 (1985). 9-Fluorenylmethyl pentafluorophenyl carbonate. 

Fluorenylmethyl pentafluorophenyl carbonate, 134 Peroxides Endoperoxides Oxygen, singlet, 228 Phenols... 

Veuthey and Haerdi reported the separation of amphetamines using packed-column SFC [26]. The amphetamines were derivatized with 9-fluorenylmethyl chloroformate and chromatographed with a methanol or 2-propanol-modified carbon dioxide as the mobil phase. The separations were compared on bare silica and aminopropyl-bonded silica columns. Both columns gave comparable results and the separation of all five amphetamines (methylamphetamine, amphetamine, phenethylamine, ephed-rine, and norephedrine) was achieved in less than 5 min. Both methanol and 2-propanol-modified carbon dioxide gave comparable results. It was observed that the modifier concentration had more effect on the solvating power than the mobile-phase density. 

Several alternative procedures have been proposed to address this serious problem, a very simple one being changes in the reaction conditions. In fact, the amount of side product is substantially reduced when a slight excess of amino acid over acylating agent (1.25 equiv) and sodium carbonate (4 equiv) are used with a minimum amount of dioxane and with vigorous stirring at room temperature. This procedure, however, cannot be applied with hydrophobic amino acids such as leucine or vahne.t l Acylation of amino acids with 9-fluorenylmethyl azidoformate (Fmoc-N3, 18, prepared from Fmoc-Cl and pre-... 

Alternative Fmoc donors have been proposed for particular purposes for example, [4-(9-fluorenylmethoxycarbonyloxy)phenyl]dimethylsulfonium methylsulfate (20) has been proposed by Okai et al. as a water-soluble reagent for the introduction of the Fmoc group in the presence of aqueous sodium carbonate. O Similarly, a polymer-bound 1,2,3-benzo-triazol-l-ol can be converted by reaction with 9-fluorenylmethyl chloroformate (17) into a polymer-bound 1,2,3-benzotriazol-l-yl 9-fluorenyhnethyl carbonate for the preparation of Fmoc-protected amines in organic and aqueous organic media with all the known advantages of insoluble reagents. ... 

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