L-4-Hydroxyproline

NucleosilChiral-I L-hydroxyproline Cu- complexes bonded on silica gel [33] Macherey-Nagel... 

For the separation of D,L-leucine, Ding et al. [62] used poly(vinyl alcohol) gel-coated microporous polypropylene hollow fibers (Fig. 5-11). An octanol phase containing the chiral selector (A-n-dodecyl-L-hydroxyproline) is flowing countercur-rently with an aqueous phase. The gel in the pores of the membrane permits diffusion of the leucine molecules, but prevents convection of the aqueous and octanol phase. At a proper selection of the flow ratios it is possible to achieve almost complete resolution of the D,L-leucine (Fig. 5-12). 

One of the first investigations related to this chemistry reported the use of a ligand which was developed by Achiwa and Ojima during the late 1970s, and was derived from L-hydroxyproline, a natural amino acid, However, for hydrogenation using this diphenylphosphino-substituted bidentate ligand, BPPM (1),... 

L-Hydroxyproline (trans), systematic name, formula, and molecular weight, 2 557t... 

V -(Fluoren-9-yhnethoxycarbonyl)-0-[4,6-di-0-acetyl-2-0-benzoyl-3-0-(2,3,4,6-tetra-0-acetyl-a-man-nopyranosyl)-a-D-mannopyranosyl]-/ra s-L-hydroxyproline Pentafluorophenyl Ester (99) [347 ... 

Of the many SO molecules investigated, derivatives of the cyclic amino acids such as L-proline (L-Pro) and L-hydroxyproline (i.-OH-Pro) are the most effective. 

Several deadly species of the genus Amanita produce colorless toxic octapeptides, the amani-tins.a b Two residues of glycine, one of L-isoleucine, one of the unusual L-dihydroxyisoleucine, one of L-asparagine, and one of L-hydroxyproline are present in a-amanitin. In the center a modified tryptophan residue has been combined oxidatively with an SH group of a cysteine residue. If the dihy-droxyisoleucine residue of a-amanitin is replaced with unhydroxylated leucine, the resulting compound, known as amanullin, is nontoxic. The LD50 for mice is 0.3 mg kg 1 and 50 g of fresh Amanita phalloides may be sufficient to kill a person. Arnan-itins act slowly, and it is impossible to kill mice in less than 15 h, no matter how high the dose. 

L-Leucine is easily extracted in quantity from almost any type of vegetable protein hyclrolyzates. Cystine is extracted from the human-hair hyclrolyzate. L-Histidine is obtainable from the blood of animals, but future yields may stem from fermentation inasmuch as some artificial mutants of bacteria have been discovered. Gelatin is the prime source of L-hydroxyproline,... 

L-Hydroxyproline incorporated as bonded phase for ligand-exchange mode separation... 

C Tao, TB Huang. Resolution of DL-a-amino acids on a L-hydroxyproline chiral phase by ligand-exchange chromatography. Chin Chem Lett 6 383-384, 1995. 

Other chiral immobilised stationary phases are available commercially, for example covalently bonded bovine serum albumin or chemically bonded l-hydroxyproline-Cu2 complexes to wide-bore Nucleosil (both from Macherey-Nagel). 

As a result of certain drawbacks attached to coated silica gel CSPs, they could not be used for preparative separations. However, the literature provides some reports on the preparative chiral separations on the bonded CSPs. The bonded CSPs are suitable for use at a preparative scale but the yield is very poor due to poor loading capacities. Davankov et al. [73] packed a column with 300 g of the L-hydroxyproline-type resin and used the chiral separation at a preparative scale. 

In dyeing the hair and the suede portion a number of factors must be allowed for. The keratin of the hair contains basically the same amino acids as the collagen of the skin but in a different ratio. The keratin of the hair includes cysteine, which cross-links the polypeptide chain and imparts stability. The collagen of the skin does not have these substances, and the cross-links are made by the tanning agent. On the other hand, only L-hydroxyproline can be found in the collagen. As a result the thermal stability is different, and in addition the isoelectric points of the two polypeptides diverge. 

Analytical Properties Chiral phases containing L-hydroxyproline as a fixed ligand show high enantio-selectivity for 2-hydroxy acids these phases have resolved some aromatic as well as aliphatic 2-hydroxy acids Reference 39... 

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