Leucine methyl ester

PEPTIDE SYNTHESES USING N-ETHYL-5-PHENYLIS0XAZ0LIUM-3 -SULF0NATE CARBOBENZOXY-l-ASPARAGINYL-l-LEUCINE METHYL ESTER AND JV-CARBOBENZOXY-3-HYDROXY-l-PROLYLGLYCYLGLYCINE ETHYL 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... 

N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-4-oylj-N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-l-oyl]-N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-l-oyl-(L-leucine methyl ester)-4-oyll-... 

Synthesis of 1-boraadamantane adducts with ethanolamine, L-phenylalanine, L-cysteine and and L-leucine methyl esters was reported (Table 3). The structures of three of them were supported by X-ray analysis (Table 1) <2003JME2823>. 

Alkylation of the 4-substituted lactone (35), derived from the (1 / )-leucine methyl ester, is an example of a very efficient 1,3-induction25. 

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

In 2004, Podlech and coworkers have reported some further advances in the photochemical treatment of Fmoc-protected diazoketones A and B, (Scheme 76), derived from leucine and alanine, respectively, with /V-(benzylidene)glycine and leucine methyl ester to produce a mixture of the corresponding diastereomeric trans-substituted p-lactams [175],... 

LME = leucine methyl ester, LEE = leucine ethyl ester,... 

Boc-L-Leucinal 1s a useful chiral synthon in the preparation of the natural amino acid statine [S-(R, R )]-4-am1no-3-hydroxy-6-methylheptanoic acid (3S.4S). The procedure reported here Is based on the method of Fehrentz and Castro for the preparation of optically active Boc amino aldehydes from a-amino acids. It Is satisfactory on a kilogram scale. Boc-L-Leucinal has also been prepared by the reduction of Boc-L-leucine methyl ester with d1Isobutyl aluminum hydride or by oxidation of Boc-L-leucinolThe reaction conditions described here differ from those In the literature. The N-... 

Introduction of R. Resin-hound amino acid ester and hydrazide Anhydrous hydrazine (2.0 mL) was added to a suspension of resin-bound N-(tert-alkylox-ycarbonyl)leucine methyl ester 53 [91] (2.07 g, 1.49 mmol) in n-butanol (8 mb) and the mixture was shaken at rt for 6.5 h. After filtration, the resin was washed alternately with THF and MeOH (four portions of each). After rinsing three times tvith CH2CI2 and drying, the resin-bound acid hydrazide (1.95 g) was obtained. 

Synthesis of N-benzyloxycarbonyl-serine-leucine methyl ester. 

Z-Leucine, methyl ester, hydrochloride [7517-19-3], 56, 89 /.-LEUCINE, N- [jV - [ (PHENYLMETH-OXY)CARBONYL] -Z-ASPARAGIN-YL]-, METHYL ESTER [14317-83-0], 56, 88... 

Continuing on this tack, Grundon and co-workers4 were able to obtain optical purities in the range of 14-22% ee. They achieved this improvement by employing 1 1 complexes of leucine methyl ester and diborane 4 in THF. Furthermore, their results were facilitated by the addition of one equivalent of BF3-etherate. Other chiral auxiliaries used include Z-valine methyl ester and p-phenylalanine methyl ester. 

For the 3,3 -dimethyl derivative 8, several other methods have been developed. The racemic 3,3 -dimethy] compound can be prepared by aminomcthylation of binaphthol with subsequent conversion of the aminomethy] function to a methyl group, and resolved analogously to binaphthol via the phosphoric acid derivative15. Another possibility is the preparation [oxidation of 3-hydroxy-2-naphthoic acid with iron(III) chloride] and resolution [with (S)-leucine methyl ester] of 2,2 -dihydroxy-1,l -binaphthyl-3,3 -dicarboxylic acid (7). 

Peptide formation with an A-protected, optically pure aminocarboxylic acid is an alternative means of obtaining diastereoisomeric derivatives of chiral aminoalkylphos-phonic acids, the diastereoisomeric products being distinguishable on a quantitative basis by P NMR spectroscopy for example, A-boc-L-alanine was used to distinguish the enantiomers of diethyl (a-aminobenzyl)phosphonate. The reaction between an enan-tiomerically enriched sample of 125 (R = H) and L-leucine methyl ester hydrochloride in the presence of DCC was followed by HPLC separation of the l,l- and D,L-peptides 126 (R = H ratio 95.3 4.7), and essentially the same procedure was applied to an analysis of 125 (R = OCH2Ph), as prepared using the bislactim ether procedure (see Section IV. C.2.b) when the final product consisted of a mixture of R,S and S,S diastereoisomers in the ratio 87.4 12.6 ... 

The caged L-leucyl-L-leucine methyl ester (140) will release L-leucyl-L-leucine... 

PEPTIDE SYNTHESES USING iV-ETHYL-6-PHENYLIS0XAZ0LIUM-3 -SULF0NATE CARB0BENZ0XY-L-ASPABAGINY1-I.-LEUCINE METHYL ESTER AND N-CARBOBENZOXY-8-HYDROXY-... 

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