Leucin Hydrochlorid

Scheme 6.44 Reaction sequence for the synthesis of enantiopure (/ )-tert-leucine hydrochloride starting from the pivalaldimine Strecker adduct obtained under catalysis with polymer-bound thiourea 41.

R)-terf-leucine hydrochloride quant, yield 84% yield overall... 

Leucine hydrochloride contains the protonated species H2L+, which can dissociate twice (Reactions 10-1 and 10-2). Because K[ = 4.70 X 10-3, H2L+ is a weak acid. HL is an even weaker acid, because K2 = 1.80 X 10 10. It appears that the H2L+ will dissociate only partly, and the resulting HL will hardly dissociate at all. For this reason, we make the (superb) approximation that a solution of H2L+ behaves as a monoprotic acid, with Ka = Kt. 

A mixture of ethyl DL-leucinate hydrochloride and ethyl orthoacetate heated 1 hr. at 75-90° ethyl N-acetyl-DL-leucinate. Y 90%. - Similarly Butylamine hydrochloride N-butylformamide. Y 85%. - By this method, N-acyl derivs. of amino acid esters can be obtained directly from easily accessible and stable hydrochlorides. S. V. Rogozhin, Y. A. Davidovidi, and V. V. Korshak, Izvest. 1970, 727 C. A. 73, 15212. 

A soln. of methyl L-isoleucyl-L-leucinate hydrochloride in dry methanol ice-salt-cooled to —10°, satd. with dry NHg, after 30 min. allowed to warm to room temp, and kept for 18 hrs. L-isoleucyl-L-leucyl anhydride. Y 74%. Also L,D-isomer and labeled compounds s. L. G. Vining, Gan. J. Ghem. 41, 2903 (1963). 

N-Benzoyl L-leucylglyclne ethyl ester (3). N-Benzoy-L-leucine 1 (0.235 g, 1 mmol) and glycine ethyl ester hydrochloride 2 (0 1534 g, 1.1 mmol) in OMF (10 mL) under stirring vyas treated with diethylphosphoryl cyanide 3 (0.179 g, 1.1 mmol) In OMF at 0°C, followed by the addition of triethylamine (0.212 g, 2 1 mmoO. The mixture was stirred for 30 min at 0°C and 4 h at 20 C The reaction mixture was diluted with PhH-EtOAc, washed with 5% HCI, water, 5% NaHCOs solution and bnne. Evaporation of the solvent gave crude 4 which after sIDca gel chromatography afforded 0.271 g of 4 (66%) (pure L), mp 1S8-160°C. 

S,N-Ditrityl-L-cysteine diethylamine selt L-Tyrosine lower alkyl ester L-lsoleucine lower alkyl ester Benzyl-L-proline hydrochloride L-Leucine lower alkyl ester Ammonia Hydrogen chloride Glycine lower alkyl ester... 

L-Leucine methyl ester hydrochloride (obtained from the Mann Research Laboratories, Inc.) was recrystallized from a mixture of methanol and ether. The recrystallized salt melted at 149-150°. 

Lead, tetrakis(acetato)- [-], 59,147 L-Leucine, methyl ester, hydrochloride [7517-19-3],56, 89 N- [A - [(phenylmethoxy)carbonyl] -L-phenylalanyl] -, methyl ester [3850-45-1],56, 93... 

The compounds investigated were the amino acids L-isoleucine, L-leucine, L-valine, and L-a-amino butyric acid. These compounds have similar molecular structures, as shown in Figure 2, and will be referred to throughout the present work as L-Ile, L-Leu, L-Val, and L-a-ABA. Where there is little likelihood of confusion, the designation L- will be omitted. Operations examined included crystallization of He through the addition of hydrochloric acid and through cooling. Under acidic conditions He crystallizes as a hydrochloride salt while in the vicinity of the isoelectric point (pH 5.2) it crystallizes as the neutral zwitterionic... 

Lead tetraacetate, 55, 44, 115 L Leucine, methyl ester, hydrochloride,... 

In this approach cysteine (19) was reduced to Cys(ol) (20) which was isolated as the triacetyl derivative 21. This compound was hydrolyzed with hydrochloric acid, the resulting hydrochloride 22 treated with 3 equivalents of NaOEt followed by addition of the a-bromo acid 24 derived from D-leucine (23). The resulting product 25 can then be /V-Boc-protected to yield the pseudodipeptide in a form suitable for solid-phase chain elongation. 

Exercises in thin-layer chromatography. Separation of amino acids. Prepare solutions of DL-alanine, L-leucine and L-lysine hydrochloride by dissolving 5 mg of each separately in 0.33 ml of distilled water, measured with a graduated 1 ml pipette (leucine may require warming to effect solution). Mix one drop of each solution to provide a mixture of the three amino acids and dilute the remainder of each solution to 1 ml to give solutions of the respective amino acids. The latter will contain about 5 pg of each amino acid per pi. Apply approximately 0.5 pi of each of the solutions to a Silica Gel G plate and allow to dry in the air (i.e. until the spots are no longer visible). 

Substrate Solution Dissolve 0.0200 g of leucine p-nitro-anilide hydrochloride (Sigma Chemical Co., Catalog No. L2158) in 100 mL of pH 7.0 Phosphate Buffer. 

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