Pipecolic adds

Another example of DKR of amines was reported by Kanerva s group in 2004. In this case, the DKR of the methyl esters of proline and pipecolic acid was based on the acylation of the secondary amino group of the amino esters with vinyl butanoate by Candida antarctica lipase A. Acetaldehyde, used as a racemising agent, was released in situ from vinyl butanoate in the presence of TEA, allowing proline and pipecolic add methyl esters to be acylated in the forms of highly enantiopure butanamides (Scheme 3.51). 

Lysine does not participate in the general deamination reactions of the amino adds. It is degraded by way of pipecolic add both in animal tissues and in plants. The steps leading from lysine to a-keb lutaric add shown in Fig. 51, have been demonstrated both in the rat and in the mould Neurospora. 

Imino-aclds.—The transformation of DL-[6- H,6- C]lysine into pipecolic add with retention of tritium has been demonstrated in rats, in Neurospora crassa, in kidney beans, and in Sedum acre, and into the piperidine alkaloid sedamine with retention of tritium in S. acre. Correspondingly, [2- H,6- C]lysine is incorporated into pipecolic acid in kidney beans and S. acre with loss of tritium, indicating that the transformation takes place via 6-amino-2-keto-hexanoic acid and A -piperideine-2-carboxylic acid. In S. acre, however. 

Extracts of crown galls from Nicotiana tabacum, Parthenocissus tricuspidata, and Scorzonera hispanica catalyse the formation of lysopine [JV l-carboxy-ethyl)lysine] from lysine, pyruvic acid, and NADH, and of octopinic acid [Af -(l-carboxycthyl)ornithine] from ornithine, pyruvic acid, and NADH. Extracts from normal tissues of the same plants are unable to catalyse the reactions.[ C]Lysine and diamino[ C]pimelic acid are incorporated into lysopine and into pipecolic acid in crown gall tissue, and it appears likely that lysine in crown gall tissue is not catabolized in the normal way, through pipecolic add or a-aminoadipic acid, but rather transferred into lysopine. 

Bugula collected in the US Virgin Islands produces by culture two cyclic tetrapeptides, microsporins A and B, which are potent inhibitors of histone deacetylase (HDAC) and cytotoxic for several human cancer cell lines (Gu et al., 2007). Microsporin A contains two nonribosomal amino acids o-pipecolic add (Pip) and 2(S)-amino-8-oxo-decanoic... 

In a similar way, D,L-pipecoUc add was converted to L-pipecolic acid [49]. However, the use of sodium borohydride, which slowly decomposes in aqueous solution, causes a significant rise in the pH value, which has to be controlled and which interferes with the necessary repeated cycles. Turner and Fotheringham expanded the applicability of the method, using milder and water stable reducing agents [50] and applying amino acid oxidases with either D- or L-spedficity. 

The structurally related alkaloid marcfortine, first described by Polonsky et al. in 1980 [35] is rendered from two isoprene units, tryptophan and pipecolic acid. The structures of the members of this family of mold metabolites are presented in Fig. 4. The paraherquamides differ with respect to substitution and oxygenation in the proline ring and the prenyiated oxindole ring paraherquamide B is the simplest member of the paraherquamide family, being comprised of the amino adds proline, tryptophan, and two isoprene units. 

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