Aminoacid unusual

The method was also applied to the synthesis of unusual aminoacids (Table 8 Y = NHAc) [83],... 

CS133 Imperato, F. N-P-coumarylglutamic acid, an unusual hydroxy cinnamic acid-aminoacid derivative from black CS143 tea. Chem Ind (London) 1980 388. 

Additional unusual steroid derivatives have been isolated from marine sponges, eg., polymastiamides, steroid/aminoacid conjugates isolated from Polymastia boletiformis, a Norwegian marine sponge [180], and an aminoimidazolium salt of steroid trisulfate from Topsentia sp. [181], Some of these marine sterols are being reproduced by chemical synthesis in the laboratory [182],... 

The unique feature of these amphibian skin opioid peptides is the sequence between the important aromatic residues. In contrast to the enkephalins and other mammalian opioid peptides that contain the Gly-Gly dipeptide sequence between Tyr and Phe, the amphibian opioid peptides contain a single D-aminoacid (see Fig. 7.41), which apparently arises from a post-translational conversion of the L-amino acid to its d isomer (665). The identification of these unusual opioid peptides expanded our understanding of the structural requirements for interaction with opioid receptors and provided new lead compounds for further modification (see Sections 6.5.1 and... 

The cytotoxic cyclic peptide, oriamide (34), containing the new 4-propenoyl-2-tyrosylthiazole unit, has been isolated from the blue marine sponge, Theonella sp., collected in Sodwana Bay [29]. This unusual aminoacid is reminiscent of the thiazole moiety early reported as a constituent of keramamide F (24) [22],... 

These peptides contain a number of unusual aminoacids including 3,4-dimethylglutamine, [5-methoxytyrosine, 3-methoxyalanine, 2,3-diaminobutanoic acid or 2-amino-2-butenoic acid residues. Papuamides are also the first natural marine-derived peptides reported to contain the 3-hydroxyleucine and homoproline residues, as well as an unprecedented acid moiety N-linked to the terminal glycine residue. Papuamide A (56) was cytotoxic against a panel of human cancer cell lines with a mean IC50 value of 75 ng/ml papuamide A (56) and B (57) inhibited the infection of human lymphoblastoid cells by HIV-1 in vitro with an EC50 of 4 ng/ml. 

The crystal structure of the HIV PR/metaUacarborane complex elucidated the binding of those unusual compounds to proteins. To comprehend the nature and properties of interactions of hetero-boranes with aminoacids and proteins, methods of molecular modeling were employed. 

It follows that the biosynthesis of this unusual aminoacid traps an high amount of cysteine. The possibility of the use of cysteine for TAU synthesis in the cat, either through the CSA or the cysteamine pathway, is therefore impaired. 

Carbon-carbon bond cleavage is important in the retro-aldol fragmentation of 2-aminoethanol and in the decarboxylation of a-aminoacids. As an example, decarboxylation in a-anilinocarboxyhc acid has been shown to be an unusually fast process (10 to 10 seer ) and to occur unimolecularly, differently from deprotonation and desilylation from structurally related anilines. The decarboxylation of the N-phthaloyl derivatives of a-amino acids has been extensively investigated (see e.g., Equation 4.21). 

Some unusual aminoacids occur in the cell walls of bacteria (Section... 

---