N-acetyl-leucine

This reaction, discovered by Sokolov and Troitskaya, ° °" allows the synthesis of enantiomers of 1,2-disubstituted ferrocenes (2.50) (pR) or (pS) (ee = 0.6). The reaction can be directed towards either of the configurations depending on the configuration of the amino acid (N-Acetyl-Leucine) used as catalyst (Figure 2.69). 

Figure 4. The FAB mass spectrum of N-acetyl leucine-enkephalin in glycerol.

Figure 5. The FAB mass spectrum of 1 1 H3/D3 N-acetyl leucine-enkephalin in glycerol -F 1 /il of oxalic acid-saturated water.

Figure 10. (a) Daughter ion MS-MS spectrum of the molecular ion of N-acetyl-leucine-enkephalin, m/z 598. (B) Daughter ion MS-MS spectrum of the molecular ion of D3 N-acetyl leucine-enkephalin, m/z 601. 

Figure 11 shows the MS-MS daughter ion spectrum obtained from the sodium adduct of N-acetyl leucine-enkephalin (MW = 619). This spectrum varies dramatically from the analogous daughter ion spectrum obtained from protonated N-acetyl leucine-enkephalin (Figure lOA). There appears to be no consistency in the... 

N-acetyl-leucine is a structural analog of N-acetyl-statine (see Fig.3 for structure), its (14) is about 600 x that for N-acetyl-statine. The same type of relationships are also observed for the Ki values of N-acetyl-valyl-statine (K = 2.8 x 10" ) and N-acetyl-Phe-Phe (K = 1 x 10 )(15) the nearest structural analog is N-acetyl-Val-Leu. No value is available, however. This unexpected potency of these competitive inhibitors fits the criteria of the "transition state" inhibitors. 

To study its mode of inhibition, we prepared several derivatives and measured their kinetics of inhibition. Both N-acetyl-statine and N-acetyl-alanyl-statine are competitive inhibitors for pepsin with values of 1.2 X lO M and 5.65 x 10 M, respectively. The value for N-acetyl-valyl-statine is 4.8 x 10 M. These statyl derivatives, therefore, are very strong inhibitors. The value for N-acetyl-statine is 600-fold smaller than that of its structural analog N-acetyl-leucine. The derivative which contains two statyl residues in a tetrapeptide exhibits inhibitory properties which approach those of pepstatin itself. Other acid proteases, human pepsin, human gastricsin, renin, cathepsin D, the acid protease from R. chinensis and bovine chymosin, also are inhibited by pepstatin and its derivatives. We suggest that the statyl residue is responsible for the unusual inhibitory capability of pepstatin and that statine is an analog of the previously proposed transition state for catalysis by pepsin and other acid proteases. 

A recent report describes the conversion of A-formyl- and N-acetyl-L-leucine into optically active azlactones with dicyclohexyl-carbodiimide (DCC) [Eq. (29)]. Other cyclization reagents, e.g. acetic anhydride, POCI3, SOCI2, and polyphosphoric acid, cause racemiza-tion. These azlactones react with optically active amino acid esters to give esters of dipeptides with retention of activity. 

PhsSnflV)] complexes of N-Ac-Gly, Af-acetyl-leucine, N-acetyl-asparagine, and N-Ac-L-Tyr were prepared by two procedures and characterized by means... 

CH2-CH(CH3)2 H9C4- Li H C4-Li/CeCl3 N-Acetyl-2-butyl-DL-leucin-methoxamid 66 75... 

S)-proline. The lithium amides of />o/> -(imino-1 -isobutylethylene) and its corresponding low-molecular-weight model compound, derived from (S)-leucine, were similarly used in order to examine the polymer effects with regard to the stereoselectivity. After acetylation, N-acetyl-a-methylphenylalanine was obtained in max. 31 % optical yield 195). 

Figure 8. Methyl-orientation results for the three methyl groups in N-acetyl-L-leucine. A, x-ray determined p(r) charge density map. B, graph showing relation between the H-C-C-H methyl torsion angles determined from the x-ray results and those determined by using a quantum chemical geometry optimization. The rms error is 8°.

C8H13N 3-ethyl-2,4-dimethyl-1 H-pyrrole 517-22-6 20.00 0.9130 1 14830 C8H15N03 N-acetyl-L-leucine 1188-21-2 25.00 1.0543 2... 

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