Hydroxyproline synthesis and

SYNTHESIS AND RU(II)-BINAP REDUCTION OF A KETOESTER DERIVED FROM HYDROXYPROLINE 2(S)-(p tert-BUTOXYCARBONYL-a-(S) and a-(R)-HYDROXYETHYL)-4(R)-HYDROXYPYRROLIDINE-1 -CARBOXYLIC ACID, tert-BUTYL... 

Dashek WV. Synthesis and transport of hydroxyproline-rich components in suspension cultures of sycamore-maple cells. Plant Physiol 1970 46 831-838. 

Inouye, K., Kobayashi, Y., Kyogoku, Y., Kishida, Y., Sakakibara, S., and Prockop, D. J. (1982). Synthesis and physical properties of (Hydroxyproline-Proline-Glycine)10 Hydroxyproline in the X-position decreases the melting temperature of the collagen triple helix. Arch. Biochem. Biophys. 219, 198-203. 

Synthesis and Ru(ll)-BINAP Reduction of a Ketoester Derived from Hydroxyproline. 

As stated earlier, only classical amino acids are built into polypeptides during amino acid polymerization, Howe er, other amino adds, classical amino acids that have been modified after incorporation into the chain, are found in proteins. >ome of the modified amino acids found in proteins are listed in Table 1.4. Vitamins ate required for the synthesis of some of the modified amino acids. For example, vitamin C is required for conversion of proiine to hydroxyproline. This and other vitamin cofactors are listed in Table T4. 

Prohne is converted back to glutamate semialdehyde, which is reduced to form glutamate. The synthesis and degradation of proline use different enzymes even though the intermediates are the same. Hydroxyproline, however, has an entirely different degradative pathway (not shown). The presence of the hydroxyl group in hydroxyproline will allow an aldolase-like reaction to occur once the ring has been hydrolyzed, which is not possible with proline. 

One of the most interesting aspects of ascorbic acid is its role in hydroxyproline synthesis (see Fig. 4-17). Connective tissue grows subcutaneously in polyvinyl sponge implants. Ascorbic acid causes rapid growth of the connective tissue under those conditions, and connective tissue proliferation is associated with a rapid incorporation of hydroxyproline. 

Figure 1. Dynamic utilization of amino acids in pigs. Degradation of essential amino acids via interorgan cooperation results in synthesis of nonessential amino acids. BCAA, branched-chain amino acids D3PG, D-3-phosphoglycerate (cm intermediate of glucose metabolism) HYP, hydroxyproline. Synthesis of serine from its carbon skeleton (D3PG) requires amino acids (e.g. aspartate and glutamate) as donors of the amino group.

Early examples of enantioselective extractions are the resolution of a-aminoalco-hol salts, such as norephedrine, with lipophilic anions (hexafluorophosphate ion) [184-186] by partition between aqueous and lipophilic phases containing esters of tartaric acid [184-188]. Alkyl derivatives of proline and hydroxyproline with cupric ions showed chiral discrimination abilities for the resolution of neutral amino acid enantiomers in n-butanol/water systems [121, 178, 189-192]. On the other hand, chiral crown ethers are classical selectors utilized for enantioseparations, due to their interesting recognition abilities [171, 178]. However, the large number of steps often required for their synthesis [182] and, consequently, their cost as well as their limited loadability makes them not very suitable for preparative purposes. Examples of ligand-exchange [193] or anion-exchange selectors [183] able to discriminate amino acid derivatives have also been described. 

Hydroxyproline-derived polyesters represent a specific embodiment of the synthetic concepts described in Fig. la. The successful synthesis of a hydroxyproline-derived polyester was first reported by Kohn and Langer in 1987 (12). Thereafter, several of these new polyesters were investigated in detail by Yu and Lange (21-23). 

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