D-leucine, 46

Lethidrone Letter acids Letterpress Letterpress printing Leucamine [81-63-0 D-leucine [328-38-1] DL-leucine [328-39-2] Leucine... 

Soluble lubricants Adipic acid d, /-Leucine Glyceryl triacetate Magnesium lauryl sulfate PEG 400, 6000, and 8000 Polyoxyethylene monostearates Sodium benzoate Sodium lauryl sulfate Sucrose monolaurate Glidants... 

Hamase, K., Inoue, T., Morikawa, A., Konno, R., Zaitsu, K. (2001). Determination of free d-proline and D-leucine in the brains of mutant mice lacking D-amino acid oxidase activity. Anal. Biochem. 298, 253-258. 

Hotchkiss114 isolated optically and analytically pure d-leucine from the hydrolysate. This was the first non-enzymatic proof that d-amino acids actually occurred in gramicidin. He also noted the presence of an amino-hydroxy compound, but indicated that it was not isoserine. 

Synge21 isolated the elusive hydroxyamino compound by azeotropic distillation and identified it as 2-aminoethanol. He proposed a structure of 6 L-tryptophane, 6 D-leucine,... 

Still using heterogeneous gramicidin, Synge24 isolated the D-leucylglycine, L-alanyl-D-valine and L-alanyl-D-leucine from partial hydrolysates of gramicidin. He also had less conclusive evidence for the tripeptides alanyl-valylleucine or alanylleucylvaline. 

Bentley et al.m recently improved upon Julia s epoxidation reaction. By using urea-hydrogen peroxide complex as the oxidant, l,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as the base and the Itsuno s immobilized poly-D-leucine (Figure 4.2) as the catalyst, the epoxidation of a, (3-unsaturated ketones was carried out in tetrahydrofuran solution. This process greatly reduces the time required when compared to the original reaction using the triphasic conditions. 

D-Leucine (7.00 g) was placed in the flask and vacuum was applied to the system. The flask was flushed with nitrogen for 1 hour and equipped with a reflux condenser. Tetrahydrofuran (85 mL) was added and the mixture heated to a gentle reflux (b.p. 65-67 °C). 

The solution remained cloudy due to the insolubility of D-leucine even when heated in tetrahydrofuran. 

The white solid was placed under high vacuum overnight to give immobilized poly-D-leucine (4.4 g) as a white powder. 

In a lOmL round-bottomed flask equipped with a magnetic stirrer bar were placed tetrahydrofuran (0.8 mL) and immobilized poly-D-leucine (100 mg). (7 )-Benzylidene acetophenone (50 mg), l,8-diazabicyclo[5.4.0] undec-7-ene (90 mg), and urea-hydrogen peroxide (27 mg) were added to the mixture. The thick white reaction mixture was stirred vigorously for 30 minutes. 

After completion, the mixture was poured into ethyl acetate and the catalyst was removed by filtration using two filter papers in a Buchner funnel. The poly-D-leucine residue was washed with ethyl acetate (2 x 10 mL), with water (2 x 10 mL) and with brine (10 mL). 

The epoxidation of enones with poly-D-leucine is complementary to other strategies. Enders et u/.[8] introduced a new method for the asymmetric epoxidation of a-enones using diethylzinc, oxygen and (1R, lR)-or (IS1, 2S)-N-methylpseudoephedrine as chiral auxiliary. 

D-Leucine, systematic name, formula, and molecular weight, 2 555t DL-Leucine, systematic name, formula, and molecular weight, 2 555t L-Leucine, systematic name, formula, and molecular weight, 2 555t Leucite, in dental ceramics, 8 275,... 

Ultrapurification of 50 mmolL DNB-D,L-Leucine in a Cascade of Five Stages with Two Modules and Two Enantiomeric Carrier (Quinine and Quinidine Derivative with 5 vol% Polysiloxane-supported Carrier) Transmembrane Material Stream J, Enantioselectivity a, Enantiomer Excess ee, Purity, and Yield of DNB-D-Leucine... 

Stage Permeate (ml h ) J (mmolh m number of stage ee (%) DNB-D-Leucine DNB-D-Leucine (% mmol)... 

Methods A Immobilised poly-(L)-leucine, urea hydrogen peroxide, DBU, THE B Immobilised poly-(D)-leucine, urea hydrogen peroxide, DBU, THE... 

In a similar fashion to those results obtained for the oxidation process, on switching from poly-(L)-leucine to poly-(D)-leucine the opposite configuration of the polyether was observed (absolute configuration of products unknown). Unexpected, however, was the observation that poly-(L)-phenylalanine furnished the opposite enantiomer to that observed employing poly-(L)-leucine. Thus, it has been shown that addition of nucleophiles other than peroxide anion can be catalysed by polyamino acids with significant stereocontrol [22]. 

The improved Julia-Colonna epoxidation conditions have been successfully employed for poly-(D)-leucine. 

Thus, epoxidation of the diene 6 using poly-(D)-leucine affords the epoxide ent-12 in 90% yield and 95% e.e. (It is worth noting at this point that the per-... 

The availability of enantiomeric catalysts (e.g. from (l) or (D)-leucine) ensures that epoxides of opposite configurations are readily accessed. 

Similarly, D-isoleucine is sweet but L-isoleucine is bitter. Both D-leucine and d-valine are sweet but their l isomers are tasteless to bitter. 

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