N-sulfonylated amino acids

The chiral allylboration reagents employed by Itsuno et al. in this study were prepared by mixing triallylborane (1 equiv) with the appropriate chiral modifier in THE A variety of chiral modifiers, including chiral diols 47 and 48, chiral hydroxy acid 49, N-sulfonylated amino acid 50, and M-sulfonylamino alcohols 51--54 was evaluated (Scheme 21). The chiral modifiers 47-54 used in this study could be prepared easily and efficiently, and were easily recovered and recycled. 

N-Sulfonyl Amino Acid Amides (Experimental Compounds]... 

N-sulfonyl amino acids have been investigated by NMR spectroscopy. NMR ligand-ligand competition experiments between Hg + and mixed donor macrobicyclic encapsulating ligands have been reported. ... 

Dansylation is often used for the determination of free and N-terminal amino acids. Dansyl chloride (5-dimethylaminonaphthalene-l-sulfonyl chloride, DNS-C1) reacts with the amino substituent of amino acids to form highly fluorescent derivatives [75,76]. The method is particularly useful for the analysis of trace components due to the high sensitivity of the products. The derivatives are usually separated by TLC on various types of layers. Separations of DNS-amino acids by flat-bed techniques have been reviewed [77]. Separations by column chromatography have been examined on polyamide [78] and Amberlite IRC-SO [79]. Although many variations of the dansylation reaction with amino acids have been reported, the one described below [77] appears to be the most common. 

Dansyl method, an approach to determination of N-terminal amino acid residues in peptides and proteins. The reagent 1 - dimethylaminonaphthalene - 5 - sulfonyl -... 

The identification of N-terminal amino acids in peptides and proteins is of considerable practical importance because it constitutes an essential step in the process of sequential analysis of peptide structures. Many N-amino acid derivatives have been proposed for this purpose and the ones most commonly studied by TLC are 2,4-dinitrophenyl (DNP)-and 5-dimethylaminonaphthalene-l-sulfonyl (dansyl, Dns)-amino acids, and 3-phenyl-2-thiohydantoins (PTH-amino acids). Recently, 4-(dimethylamino)azobenzaie-4/-isothio-cyanate (DABITC) and phenyl-isothiocyanate (PITC) have also been investigated as derivatizing agents of amino acids. 

Another method for determining the identity of the N-terminal amino acid is to react the peptide with dimethylaminonaphthalenesulfonyl chloride (183, known as dansyl chloride). When 183 reacts with a peptide such as 179, the amine unit reacts with the sulfonyl chloride to give the sulfonamide... 

Shai and Patchornik showed that poly(sulfonyl chloride) (prepared by chlorosulfonation of a macroporous resin) is an excellent reagent for the formation of 1-hydroxybenzotriazole (HOBt) esters of N-blocked amino acids, as in Scheme 41. 

This sulfonyl urea, prepared from an amino acid and p-tosyl isocyanate in 20-80% yield, is cleaved by alcohols (95% aq. EtOH, n-PrOH, or -BuOH, 100°, 1 h, 95% yield). It is stable to dilute base, to acids (HBr/AcOH or cold CF3CO2H), and to hydrazine. ... 

A series of chiral boron catalysts prepared from, e.g., N-sulfonyl a-amino acids has also been developed and used in a variety of cycloaddition reactions [18]. Corey et al. have applied the chiral (S)-tryptophan-derived oxazaborolidine-boron catalyst 11 and used it for the conversion of, e.g., benzaldehyde la to the cycloaddition product 3a by reaction with Danishefsky s diene 2a [18h]. This reaction la affords mainly the Mukaiyama aldol product 10, which, after isolation, was converted to 3a by treatment with TFA (Scheme 4.11). It was observed that no cycloaddition product was produced in the initial step, providing evidence for the two-step process. 

A-Acido imines (R R"C = N —X=0) like /V-acyl (X = CR) /V-sulfonyl [X = S(R)=0]2-7 or /V-diphenylphosphinoylimines [X = P(C6H5)2]3 are masked inline derivatives of ammonia. Compared to the imines themselves these activated derivatives are better electrophiles showing less tendency to undergo undesired deprotonation rather than addition of organometal-lics1812 The apparent advantages of these compounds have been exploited for asymmetric syntheses of amines, amides, amino acids and /J-lactams1-8 I6. 

For the sulfonation step, amino acids were added as their sodium salts. The reactions were carried out in cold aqueous solution, in which the sulfonamides were immediately precipitated. By the same method dansylations of amino acids could be accomplished with N-( 1 -dimethylaminonaphthalene-5-sulfonyl)-Af -methylimidazolium chloride ... 

Besides Ir-diphosphines, two more catalyst systems have shown promise for industrial application. As mentioned in Section 37.5.2, the Rh-Josiphos-cata-lyzed hydrogenation of unprotected /1-dehydro amino acid derivatives by Merck actually involves the hydrogenation of a C=N and not a C=C bond (see Fig. 37.10) [3, 51]. Noyori s Ru-PP-NN catalyst system seems also suitable for C=N hydrogenation [129], and was successfully applied in a feasibility study by Dow/Chirotech for the hydrogenation of a sulfonyl amidine [130]. Avecia also showed the viability of its CATHy catalyst for the transfer hydrogenation of phosphinyl imines [115] (see Fig. 37.34). 

Increasing interest is expressed in diastereoselective addition of organometallic reagents to the ON bond of chiral imines or their derivatives, as well as chiral catalyst-facilitated enantioselective addition of nucleophiles to pro-chiral imines.98 The imines frequently selected for investigation include N-masked imines such as oxime ethers, sulfenimines, and /V-trimcthylsilylimines (150-153). A variety of chiral modifiers, including chiral boron compounds, chiral diols, chiral hydroxy acids, A-sull onyl amino acids, and /V-sulfonyl amido alcohols 141-149, have been evaluated for their efficiency in enantioselective allylboration reactions.680... 

Further studies concerning aza Diels-Alder reactions of N-sulfonyl imines have been carried out by Holmes et al. [200] and Whiting et al. [201,202], and the utility of glyoxylato imines for the synthesis of cyclic amino acids has been investigated by Stella s group [203, 204]. An extensive study concerning intramole-... 

Tribenuronmethyl (Sulfonyl urea) CO.CH, OCH, n C >-SOjNHCON—< N CH- CHj Branched chain amino acid synthesis (ALS and A HAS) inhibitor. Acts by inhibiting biosynthesis of the essential amino acids valine and isoleucine, hence stopping cell division and plant growth... 

Reactions of A/-amino compounds with electrophiles. Af-Aminopyridinium cations can be acylated or sulfonylated (with acid halides) and nitrated (H2SO4-HNO3) to give the corresponding N-(substituted amino)pyridines, often isolated as the imides (1014 R = COR, S02R, or N02). 

Triethylamine (8) Ethanamine, N,N-diethyl- (9) (121-44-8) p-Toluensulfonyl chloride (8) Benzenesulfonyl chloride, 4-methyl- (9) (98-59-9) (lS,2S)-2-(N-Tosylamino)cyclohexanecarboxylic acid Cyclohexanecarboxylic acid, 2-[[(4-methylphenyl)sulfonyl]amino]-, (1S-trans)- (12) (110456-11-6)... 

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