Carbamates, derivatized

Another study focused on aryl-substituted P-lactams, using the same set of teicoplanin-based CSPs and variable-temperature conditions [99]. Tricyclic P-lactams were investigated by the same group of authors, together with some bicyclic P-amino acids, on five different commercially available glycopeptides CSPs, namely ristocetin A, TE, TAG, vancomycin, and VAG, and on a new dimethylphenyl carbamate-derivatized 5-cyclodextrin-based CSP. The chromatographic results, achieved with different methods, were compared in systematic examinations [170]. 

S Cladrowa-Runge, A Rizzi. Enantioseparations of 6-aminoquinolyl-lV-hydrox-ysuccinimidyl carbamate derivatized amino acids by capillary zone electrophoresis using native and substituted /3-cyclodextnns as chiral additives II. Evaluation of complexation constants. J Chromatogr A 759 167-175, 1997. 

C van Wandelen, SA Cohen. Using quaternary high-performance liquid chromatography eluent systems for separating 6-aminoquinolyl-V-hydroxysuccinimidyl carbamate-derivatized amino acid mixtures. J Chromatogr A 763 11-22, 1997. 

SA Cohen, C Van Wandelen. Amino acid analysis of unusual and complex samples based on 6-aminoquinolyl-V-hydroxysuccinimidyl carbamate derivatization. Techniques in Protein Chemistry VIII 185-196, 1997. 

Amino Acid Analysis of Unusual and Complex Samples Based on 6-aminoquinolyl-N-hydroxysuccinimidyl Carbamate Derivatization... 

Although some of the early work on the separation of diastereomers by GLC (71) or LC (19) involved carbamates, derivatization of chiral amines with chloroformate CDAs has received relatively little attention until recently in pharmaceutical/pharmacological applications. This is surprising, inasmuch as chiral chloroformates can be readily synthesized from chiral alcohols, many of which are commercially available. There are indications, however, that interest in the use of chloroformates is increasing, and several reports on such reagents have appeared in recent years. 

Carbonic Acid Derivatives on Resin Carbamate derivatization of some common hydroxy resins (i.e. hydroxymethylpolystyrene, Wang or the oxime resins) has also been described for the synthesis of ureas, sulfonamides and dihydropyri-... 

Figure 15.3 Urea and sulfonamide synthesis from carbamate derivatized oxime (19), thiophenol (16) and Wang (4) resins.

The Separation of a Pair of Enantiomers on a Carbamate Derivatized Cellulose-Type Stationary Phase Using Both the Reversed Phase and Normal Phase Mode... 

D.W. Armstrong, M. Hilton and L.Coffm, Multimodal Chiral Stationary Phases for Liquid Chromatography (R)- and (S)-Naphthylethyl-carbamate-Derivatized Cyclodextrin, LC.GC, 9(9)(1991) 646. 

Another example of curvature of van t Hoff plots relates to irreversible changes in the conformation of carbamate-derivatized amylose and cellulose CSP, which was observed for the normal-phase separation of the enantiomers of a dihydropyrimidinone acid and methyl ester. The apparent conformational change was thermally induced and depended upon the polar component of the mobile phase. The irreversible change in the conformation of... 

Armstrong (142) published a work focusing on the use of the macrocyclic antibiotic vancomycin as a chiral mobile phase additive. In this work the separations of carbamates, derivatized amino acids, racemic drugs and dansylamino acids were performed on diphenyl modified stationary phases with the eluent systems acetonitrile-0.6 M NaCl-1% triethylammonium acetate buffer (pH 4.1). 

Fig. 8 Separation of tra 5 -l-amino-2-indanol on a methyl carbamate derivatized CF6 CSP (column 25 cm,...

Table 1 The effect of add and basic additives on the chromatographic sepeiration of ( ) trans-l-amino-2-indanol in the polm oigtinic mode on an isopropyl carbamate derivatized CF6 25 cm x 4.6 column...

Fig. 9 Separation of tran -l-amino-2-indanol (Z ) and Troger s base right) on CF6 CSPs (columns 25 cm, 4.6 mm i.d.) derivatized in three different ways (a) and (d), low-degree methyl carbamate derivatization (b) and (e), low-degree 3,5-dimethylphenyl carbamate deriva-tization (c) and (f), high-degree 3,5-dimethylphenyl carbamate derivatization. Mobile phases left, acetonitrile/methanol/acetic acid/triethylamine 60/40/0.3/0.2 (70/30/0.3/0.2% v/v for (c)) right, heptane/ethanol 10130% v/v and 1 mL/min. UV detection 254 nm...

Ten different aromatic derivatizations of CF6 were made. Examples of the enantiomeric separation of different classes of racemates are shown in Fig. 11. Most of the observed enantiomeric separations could be obtained on several different aromatic-derivatized CSPs [39]. In addition, the same elution order is generally obtained for chiral compounds on R- and S-naphthylethyl carbamate derivatized CSPs. These observations suggest that the enantiomeric selectivities of the aromatic-functionalized CF6 CSPs are more dependent on the chirality of the base CF6 than on the chirality of substituent groups. However, aromatic moieties play an indispensable role in chiral recognitions because the separations of non-primary amine compounds on aromatic-derivatized CF6 CSPs are generally better than those on aliphatic-derivatized ones. 

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