A comprehensive review of chemistry and pharmacological aspects of natural cyanobacterial azoline-based circular and linear oligopeptides

Thirtieth Anniversary of the Discovery of Laxaphycins. Intriguing Peptides Keeping a Part of Their Mystery

“…The 3-hydroxyasparagine was stereochemically (2R,3R). An alternation of L and D stereochemistry can be seen along the peptide sequence, with (3R)-Ade 1 , (2R,3S)-3-OH-Leu 5 , (2R,3R)-3-OH-Asn 8 and D- Leu 11 , and the hydrophobic/hydrophilic character of amino acids is also alternated within the sequence. A further study of the biological activities of laxaphycins produced by cyanobacteria was carried out by the same group in 2007, giving rise at the same time to two new laxaphycins named laxaphycins B2 and B3 (Figure 1) [22].…”

“…On the scytocyclamide B side, the LxaI i -L i modules continue the elongation. The modules LxaI 2 , LxaJ 1 , LxaJ 3 , and LxaK 4 additionally have an epimerization domain E to give an absolute configuration D on the amino acids Leu 3 , Leu 5 , Asn 8 , and Leu 11 , respectively. LxaJ 3 also has an N-methylation domain to obtain N-methylisoleucine in position 7.…”

“…The enzymes LxaF-G and LxaM were identified as cupin-like domain proteins and would be involved in the hydroxylation of Aoc 1 , Leu 3 , and Hse 8 . The adenylation domains corresponding to Hle 3 and Leu 5 being identical, they would be specific to leucine and the hydroxylation of Leu 3 would occur later, either while it is bound to the PCP or after the release of the peptide.…”

“…These marine natural products can be used in applications such as drugs in the fight against cancer, virus, or bacterial infections but also as cosmetics [1][2][3][4]. Cyanobacteria that represent at least 50% of the aquatic biomass are effective producers of secondary metabolites that can be used as therapeutic agents [5][6][7][8], among which peptides isolated from various strains all over the world [9]. These peptides are often synthesized by non-ribosomal peptide synthetase (NRPS) or mixed biosynthetic pathways that involve polyketide synthase (PKS) operating in conjunction with NRPS [10][11][12].…”

Synthesis, In Silico and In Vitro Evaluation of Antimicrobial and Toxicity Features of New 4-[(4-Chlorophenyl)sulfonyl]benzoic Acid Derivatives

“…In this study, we started from the premise that the 1,3-oxazole nucleus is an important scaffold in synthetic, pharmaceutical, and medicinal chemistry, with a remarkable versatility that results in a high structural diversity. Also, it is well known that numerous naturally occurring heterocycles bearing 1,3-oxazole cores are bioactive substances, exhibiting many biological properties [ 3 , 4 , 5 , 6 , 7 ], of which it is worth mentioning their antibacterial (e.g., almazole D, muscoride A), antifungal (e.g., bengazole A, mycalolide A), antiviral (e.g., hennoxazole A), and antiproliferative (e.g., bistratamide M and N, diazonamides A–E) properties. The structures of representative naturally occurring bioactive compounds sharing the 1,3-oxazole template are presented in Figure 1 .…”