N- a-amino

Carbohydrate-derived titanium cnolates also provide yvn-x-amino-/l-hydroxy esters of high diastcrcomeric and enantiomeric purity. For this purpose, the lithium enolate derived from ethyl (2,2,5,5-tetramcthyl-2,5-disilapyrrolidin-l-yl)acetate is first transmctalated with chloro(cy-clopentadienyl)bis(1,2 5,6-di-0-isopropylidene-a-D-glucofuranos-3-0-yl)titanium and subsequently reacted with aldehydes.. vj-n-a-Amino-/ -hydroxy esters are almost exclusively obtained via a predominant /te-side attack (synjanti 92 8 to 96 4 87-98% ee for the xvn-adducts)623-b. 

Thioessigsaure wirkt auf Benzoesaure-amid-hydroximid uur acylierend unter Bildung von 0-Acetvl-N-(a-amino-benzyliden)-hydroxylaminno. Aus 4-(Amino-hydroximino-methyl)-5-oxo-2,2,3-trimethyl-2,5-dihydro-furan entsteht in siedender Essigsaure das N-Acetyl-Derivat I82, das unter diesen Bedingungen nicht zum 1,2,4-Oxadiazol cyclisiert. 

Die Umsetzung von Benzoesaure-amid-hydroximid mit Keten in benzolischer Losung bei 0° licfert nur das primare Additionsprodukt 0-Acety]-N-(a-amino-benzyliden)-hydroxylamin in 82% Ausbeute116. 

D-Glucose h-lysine. HCl (millimoles) pH Total N a-Amino Na Color... 

N-a-Amino acids (10 mg) were typically dissolved in 200 mM, pH 10 sodium metaborate buffer (1 ml), and methylated directly by the addition of a 1 1 v/v solution (20 gl) of [ C]iodomethane in acetonitrile, with rapid mixing of the sealed biphasic mixture at 37°C for 24 h. Cystine dimethyl ester, in particular, was first converted to the diamide at pH 9.5 using ammonia. Histidine amide was first acetylated prior to reaction with iodomethane. 

Since the process represented by reactions (4a) and (4b) is a simple addition polymerization it leads to a distribution of molecular weights of the Poisson type [2]. At any st e of the reaction the concentration of polymer molecules containing n a-amino acid units [P ] is given by... 

If N a-amino acids are converted into the corresponding peptides, at least 3N -1 steps of preparative procedures must occur in order to protect, connect and deprotect the functional groups of the a-amino acids. 

The influence of a large number of oc-amino acids on the values of and k at have been determined. These a-amino acids included glycine, L-valine, L-leucine, L-phenylalanine, L-tyrosine, L-tryptophan, NOrmethyl-L-tryptophan (L-abrine), N-methyl-L-tyrosine, N,N-dimethyl-L-tyrosine and p -me thoxy-N-me thyl -L -phenyl al anine. 

The most suitable synthetic method for these products is the heterocyc-lization reaction of N-thioacyl derivatives of amino acids (202) with phosphorus tribromide (378, 442-450, 559, 560) or anhydrous trifluoroacetic acid (448, 449, 451, 452) (Scheme 103). Treatment of N-thioacyl amino acids with acetic anhydride leads directly to the thiazolylacetate without isolation of an intermediate thiazolinone (365. 452). 2-Alkoxy-derivatives of A-2-thiazoline-5-one, however, can be obtained without acetylation by this method (453, 454). 

TABLE n-36. 2,5-DIAMINOTHIAZOLE DERfVATIVES FROM a-AMINO-NITRILES AND ISOTHIOCYANaTES. 

Edman degradation (Section 27 13) Method for determining the N terminal amino acid of a peptide or protein It in volves treating the material with phenyl isothiocyanate (CgH5N=C=S) cleaving with acid and then identifying the phenylthiohydantoin (PTH derivative) produced Elastomer (Section 10 11) A synthetic polymer that possesses elasticity... 

P-Endorphin. A peptide corresponding to the 31 C-terminal amino acids of P-LPH was first discovered in camel pituitary tissue (10). This substance is P-endorphin, which exerts a potent analgesic effect by binding to cell surface receptors in the central nervous system. The sequence of P-endorphin is well conserved across species for the first 25 N-terminal amino acids. Opiates derived from plant sources, eg, heroin, morphine, opium, etc, exert their actions by interacting with the P-endorphin receptor. On a molar basis, this peptide has approximately five times the potency of morphine. Both P-endorphin and ACTH ate cosecreted from the pituitary gland. Whereas the physiologic importance of P-endorphin release into the systemic circulation is not certain, this molecule clearly has been shown to be an important neurotransmitter within the central nervous system. Endorphin has been invaluable as a research tool, but has not been clinically useful due to the avadabihty of plant-derived opiates. 

Rearrangement of N.N-dimethyttiydrazone or tosylate derivatives of oxime to azirines and from there to a-amino ketones. 

The Tcrom ester is prepared from the cesium salt of an N-protected amino acid by reaction with 2-(trifluoromethyl)-6-chromylmethyl bromide (DMF, 25°, 4 h, 53-89% yield). Cleavage of the Tcrom group is effected by brief treatment with n-propylamine (2 min, 25°, 96% yield). It is stable to HCl/dioxane, used to cleave a BOC group. ... 

The bulky triphenylmethyl group has been used to protect a variety of amines such as amino acids, penicillins, and cephalosporins. Esters of N-trityl a-amino acids are shielded from hydrolysis and require forcing conditions for cleavage. The a-proton s also shielded from deprotonation, which means that esters elsewhere in the molecule can be selectively deprotonated. 

Acetyl-a-amino-n-butyric acid [34271-24-4] M 145.2, pK 3.72. Crystd twice from water (charcoal) and air dried [King and King J Am Chem Soc 78 1089 7956]. 

One of the historically most significant examples of aromatie nueleophilie substitution is the reaetion of amines with 2,4-dinitrofluorobenzene. This reaetion was used by Sanger to develop a method for identifieation of the N-terminal amino acid in proteins and the proeess opened the way for struetural eharacterization of proteins and other biopolymers. 

---