Di-Valine

Predict the product of the reaction of valine with the following reagents (a) CH3CH2OH, acid (b) Di-fert-butyl dicarbonate... 

CN stereoisomer of /V,iV-[(2-amino-4,6-dimethyl-3-oxo-377-phenoxazine-l,9-diyl)bis[carbonylimino[2-( 1 -hydroxyethyl)-1 -oxo-2,1 -ethanediyl]imino[2-( 1 -methylethyl)-1 -oxo-2,1 -ethanediy 1]-1,2-pyrrolidinediylcarbonyl(methylimino)(l-oxo-2,l-ethanediyl)]]bis[A/-methyl-L-valine] di- -lactone... 

Fig. 22.4. Model of aciclovir and Val-aciclovir transport. The prodrug Val-aciclovir is taken up at the apical cell membrane via the di/tri-peptide transporter, hydrolyzed intracelIularly in the enterocyte, with basal exit of valine and aciclovir. (Adapted from Smith et a. [78].)...

As an example of the way in which the code is read. Fig. 2 shows small sections from the normal and a mutated form of the P-globin gene (see p. 280), as well as the corresponding mRNA and protein sequences. The point mutation shown, which is relatively frequent, leads to replacement of a glutamate residue in position 6 of the p-chain by valine (GAG GTG). As a consequence, the mutated hemoglobin tends to aggregate in the deoxy-genated form. This leads to sickle-shaped dis-... 

The numerous preparations of mono-, di-, tri-, and hexafluoro derivatives of valine, norvaline, leucine, norleucine, and isoleucine, using classical methods of amino acid chemistry (e.g., amination of an a-bromoacid, " azalactone, Strecker reaction, amidocarbonylation of a trifluoromethyl aldehyde, alkylation of a glycinate anion are not considered here. Pure enantiomers are generally obtained by enzymatic resolution of the racemate, chemical resolution, or asymmetric Strecker reaction. ... 

Gibson KM, Lee CF, Bennett MJ, Holmes B, Nyhan WL (1993) Combined malonic, methylmalonic and ethylmalonic acid semialdehyde dehydrogenase deficiencies an inborn error of beta-alanine, L-valine and L-alloisoleucine metabolism J Inherit Metab Dis 16 563-567... 

The separation of enantiomers can be effected either by transforming them into diastereoisomers using a chiral reagent and separating them on conventional phases or by separating the enantiomers on chiral phases. The utilization of chiral phases has not yet become routine, but studies of enantiomeric dipeptides have been carried out (115,116). Pirkle et al. (117) and Hyun et al. (118) separated enantiomeric di- and tripeptides (methyl esters of /V-3-5-dinitrobenzoyl derivatives) on chiral stationary phases (CSPs) derived from (R)-a-arylalkylamines, (S)-N-(2-naphthyl) valine, or (S)-1 -(6,7-dimethyl-1 -naphthyl) isobutylamine. These workers were able to separate four peaks for each dipeptide derivative, corresponding to the two enantiomeric pairs (R,R)/(S,S) and (R,S)/(S,R). Cyclodextrin-bonded stationary phases and chiral stationary immobilized a-chymotrypsin phases were used to separate enantiomeric peptides (118a,b). 

Rodgers and Jacobson77 have published the crystal structure of DL-(ethyl valinate-JV,iV-di-acetato)diaquacopper(II), the copper(II) complex of EVDA (14c). The stereochemistry around copper is distorted octahedral, the equatorial coordination sphere consisting of the tertiary... 

Following the dipeptide synthesis from O-methyl-serine and Val by determining the loss 180 from di[180]valine, evidence for both reactions was obtained, but a direct reaction of Cys-AMP with free Val cannot be excluded [reaction (15)]. 

A final comment on Table 4 concerns the reaction shown in entry 8. Because the di-TT-methane photorearrangement of benzonorbomadiene derivatives requires triplet energy sensitization, we could not use typical, passive amines such as (/ )-( + )-l-phenylethylamine as chiral auxiliaries. We therefore prepared an optically pure amine to which a sensitizing benzophenone moiety was tethered, namely, the 4-benzoylphenyl ester of l-valine [25]. Photolysis of the salt of this amine at wavelengths where only the benzophenone chromophore absorbs led to the photoproduct in 91% ee at 100% conversion, a gratifying vindication of the concept. Optically active photosensitizers have been used in solution with limited success [33], but this represents the first example of simultaneous triplet-triplet energy transfer and asymmetric induction in the crystalline state. 

Salt crystals of the benzonorbomadiene carboxylic acid 68 with optically pure triplet sensitizer amines 70, 71 also underwent enantioselective di-TT-meth-ane photorearrangement to afford the optically active tetracyclo[5.4.0.02,4.03 6]undecane derivative 69 in high enantiomeric excess [81]. The 4-acetylbenzyl ester of L-phenylalanine 70 and the 4-benzoylphenyl ester of l-valine 71 perform the dual roles of asymmetric induction and triplet energy sensitization. 

DLSERN11. D,L-Serine (neutron study) (C3H7N03). Frey MN, Lehmann MS, Koetzle TF, Hamilton WC (1973) Acta Crystallogr, Sect B 29 876 DLTYRS. D,L-iyrosine (CgHnNO. Mostad A, Romming C (1973) Acta Chem Scand 27 401 DLVALC. D,L-Valine hydrochloride (C5H12NO, Cl-). Di Blasio B, Napolitano G, Pedone C... 

Although the asymmetric aldol reaction of benzaldehyde and di ketene has been reported with a catalyst generated from di-iso-propyl tartrate and iso-propanol, low induction and low yields were observed for the d-hydroxyl-y5-keto ester 27 [8], Low induction was also observed for aldol reactions mediated by chiral aluminum catalysts generated from a-amino acids [9]. These types of catalyst have been very successful when employing boron as the Lewis acid, as illustrated in the aldol reaction of ketene acetal 10 with the boron catalyst 31 derived from (5)-valine (Sch. 4) [9,10]. Catalysts derived from A-tosyl-(5 )-valine and Et2AlCl and i-BuyAl were relatively ineffective (< 15 % ee) [9]. 

C20H14S2 di-1-naphthyl disulfide 39178-11-5 20.00 1.1440 1 32149 C20H21NO4 fmoc-L-valine 68858-211 2lll 11878 31... 

The essentially complete assignment of H, 13C and 15N resonances of recombinant human ubiquitin were obtained by analysis of HNCA, HN(CO)CA, HNCO and HCCH-TOCSY spectra and reference to previously reported H (Di Stefano and Wand, 1987) and 15n (Schneider et al., 1992) resonance assignments (Wand et al., 1996). Stereospecific assignments of leucine 5-CH3 and valine y-CHj groups were obtained using the isotopic labeling strategy developed by Neri et al. (1990). This approach provided unequivocal prochiral... 

PEPT1 (SLCISAI) Human Glycylsarcosine, di-, tripetides Drugs p-lactam antibiotics, cyclacillin, valacyclovir Valine, pentaglycine Drugs p-lactam antibiotics, bestatin, certain ACE inhibitors... 

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