Amino acid lithium salt

Benzenesulfonyl chloride, 4-methyl- [p-Tol-uenesulfonyl chloride], 55, 57, 59 Benzenethiol [Phenol, thio-], 55, 122 Benzenethiol, copper(I) salt [Thiophenol, copper(I) salt], 55, 123 Benzenethiol, lithium salt [Thiophenol, lithium salt], 55, 1 22 Benzoic acid, 2-amino- [Anthramlic acid], p bromination of, 55, 23... 

Alkaline hydrolysis with barium, sodium, or lithium hydroxides (0.2-4 M) at 110°C for 18-70 h126-291 requires special reaction vessels and handling. Reaction mixtures are neutralized after hydrolysis and barium ions have to be removed by precipitation as their carbonate or sulfate salts prior to analysis which leads to loss of hydrolysate. Correspondingly, peptide contents are difficult to perform by this procedure. Preferred conditions for alkaline hydrolysis are 4M LiOH at 145 °C for 4-8 h where >95% of tryptophan is recovered 291 An additional inconvenience of the alkaline hydrolysis procedure is the dilution effect in the neutralization step and thus the difficult application to the analyzer if micro-scale analysis is to be performed. The main advantage is the good recovery of tryptophan and of acid-labile amino acid derivatives such as tyrosine-0-sulfate1261 (Section 6.6) as well as partial recovery of phosphoamino acids, particularly of threonine- and tyrosine-O-phosphate (Section 6.5). 

Amino acids can be separated without prior derivatization on a cation-exchange resin column. The elution buffers are classically lithium citrate buffers with different pH values and salt concentrations, which are applied stepwise. There is usually a programmed increase in column temperature. Consequently, there are numerous variables affecting the separation of the individual amino acids [6]. For the detection of the amino acids, the column effluent is mixed with the ninhydrin reagent. Nowadays there are only very few manufacturers of AAAs left. The considerable cost of purchase and the operation costs are a potential threat to the widespread application of this technique, although it is still considered to be the definitive method for diagnosing disorders of amino acid metabolism. 

Three methods for making 4,5,6,7-tetrahydrotriazoIopyridines use two fragments to form the triazole ring. The lithium derivative of A/-nitro-sopiperidine reacts with benzonitrile to give the 3-phenyl derivative 19.28 Diazonium salts react with a-amino acids to give mesoionic triazole oxides if pipecolic acid is used, the product is a tetrahydrotriazolopyridine 3-oxide... 

Horner-Emmons reaction of N-terminal blocked aldehyde 1 with sulfonylphosphonates in the presence of sodium hydride gives the amino acid vinyl sulfone 2, which is deprotected with acid and converted into its chloride or tosylate salt 3 and coupled by the mixed anhydride method with an N-terminal protected peptide or amino acid to give the desired peptide vinyl sulfones 4 (Scheme 2). 4 5 N-Terminal protected aldehydes 1 are obtained from reduction of Boc amino acid V-methoxy-A-methylamides (Weinreb amides, see Section 15.1.1) by lithium aluminum hydride. 9 The V-methoxy-V-methylamide derivatives are prepared by reaction of Boc amino acids with N,O-dimethylhydroxylamine hydrochloride in... 

Using this method, several mesogen diacetylenes were obtained [49]. Palladium-catalysed coupling of an allylic cyclic carbonate with 1-pentynyl phenyliodonium tetrafluoroborate to give an enyne was highly successful [50]. Alkynyl iodonium triflates and lithium salts of diethyl 2-[(diphenylmethylene)amino]malonate were used for the preparation of alkynyl-a-amino acid derivatives, e.g. [51] ... 

The most versatile method of preparing a-azidocarboximides2 and protected a-amino acids is based on early investigations3. In this study the lithium enolate 2 of the azetidinone 1 [prepared with lithium diisopropylamide (LDA)] is treated with tosyl azide to afford an adduct 3, isolated and characterized by IR spectroscopy as the lithium salt of an acyclic triazene3. 

Summary Treatment of geminal silyldiamines with monohalo silanes leads to the formation of 1-amino-1,3-disilazanes. Mono-NH-SiF-functional cyclodisilazanes can be isolated by ring closure of their lithium derivatives in the reaction with trifluorosilanes. Lithium salts of these cyclodisilazanes react with H-acidic compounds like alcohols as amides and with unsaturated compounds like aldehydes as silaimines. 

---