Synthesis of New Lipophilic Phosphonate and Phosphonamidate Analogues of N-Acetylmuramyl-L-alanyl-D-isoglutamine Related to LK 423

Synthetic strategies of phosphonodepsipeptides

Phosphonodepsipeptides are phosphorus analogues of depsipeptides and phosphonate-linked analogues of naturally occurring peptides. They are more stable than phosphonopeptides and have been widely applied as enzyme inhibitors, haptens for the production of antibodies, biological agents, and prodrugs. The synthetic strategies towards phosphonodepsipeptides are reviewed, including the phosphonylation of hydroxy esters with phosphonochloridates, the condensation of phosphonic monoesters and hydroxy esters, the alkylation of phosphonic monoesters with 1-(alkoxycarbonyl)alkyl halides or sulfonates, multicomponent condensation of amides, aldehydes, and dichlorophosphites followed by alcoholysis with hydroxy esters, the phosphinylation of hydroxy esters with phosphonochloridites followed by oxidation, and the carbene insertion of N-protected amino acids with 1-diazoalkylphosphonates. This review includes the synthesis of α-, β-, and γ-phosphonodepsipeptides and phosphonodepsipeptides with C-1-hydroxyalkylphosphonic acids.

Synthetic Methods of Phosphonopeptides

Phosphonopeptides are phosphorus analogues of peptides and have been widely applied as enzyme inhibitors and antigens to induce catalytic antibodies. Phosphonopeptides generally contain one aminoalkylphosphonic acid residue and include phosphonopeptides with C-terminal aminoalkylphosphonic acids and phosphonopeptides with a phosphonamidate bond. The phosphonamidate bond in the phosphonopeptides is generally formed via phosphonylation with phosphonochloridates, condensation with coupling reagents and enzymes, and phosphinylation followed by oxidation. Pseudo four-component condensation reaction of amides, aldehydes, alkyl dichlorophosphites, and amino/peptide esters is an alternative, convergent, and efficient strategy for synthesis of phosphonopeptides through simultaneous construction of aminoalkylphosphonic acids and formation of the phosphonamidate bond. This review focuses on the synthetic methods of phosphonopeptides containing a phosphonamidate bond.

Synthesis of potent and broad genotypically active NS5B HCV non-nucleoside inhibitors binding to the thumb domain allosteric site 2 of the viral polymerase

The hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase (RdRp) plays a central role in virus replication. NS5B has no functional equivalent in mammalian cells and, as a consequence, is an attractive target for selective inhibition. This Letter describes the discovery of a new family of HCV NS5B non-nucleoside inhibitors, based on the bioisosterism between amide and phosphonamidate functions. As part of this program, SAR in this new series led to the identification of IDX17119, a potent non-nucleoside inhibitor, active on the genotypes 1b, 2a, 3a and 4a. The structure and binding domain of IDX17119 were confirmed by X-ray co-crystallization study.

Cloning, sequencing, and heterologous expression of an Erwinia cypripedii 314B lactonase specific for L-alpha-hydroxyglutaric acid gamma-lactone

The gene for a lactonase that stereospecifically hydrolyzes (S)-5-oxo-2-tetrahydrofurancarboxylic acid to L-alpha-hydroxyglutaric acid was isolated from Erwinia cypripedii 314B. Determination of the nucleotide sequence showed that the gene consists of a single open reading frame of 1,152 bp that encodes a 383-amino-acid protein. Comparison of the sequence of the predicted protein to that of the enzyme purified from E. cypripedii 314B revealed an N-terminal signal sequence of 19 amino acids. The gene for the mature enzyme was inserted into a pET vector and overexpressed in Escherichia coli. Active recombinant enzyme accumulated in the cells to approximately 30% of the total protein, and the enzyme was purified to homogeneity. The physical and catalytic properties of the recombinant enzyme were indistinguishable from those of the protein purified from E. cypripedii 314B. The deduced amino acid sequence displayed approximately 35% similarity with a putative 3-carboxymuconate cyclase, but exhibited no such activity. The enzyme also showed approximately 35% similarity with 6-phosphogluconolactonase. However, the activity of the enzyme toward 6-phosphogluconolactone was less than 2% of that toward (S)-5-oxo-2-tetrahydrofurancarboxylic acid, demonstrating a novel specificity for this lactonase.

Modulation of cytokine production by some phthalimido-desmuramyl dipeptides and their cytotoxicity

Muramyl dipeptide (MDP) is the smallest bacterial cell wall peptidoglycan component having immunomodulatory activity. In an attempt to obtain MDP derivatives with improved and better defined pharmacological profiles we synthesized a new lipophilic phthalimido-desmuramyl dipeptide, LK 508. This novel MDP analogue and three structurally related phthalimido-desmuramyl dipeptides (LK 413, LK 511 and LK 512) were evaluated immunologically. Their ability to modulate the production of cytokines was measured in vitro by their inclusion in cultures of human peripheral blood mononuclear cells (PBMC) activated by ionomycin and phorbol-12-myristate-13-acetate (PMA). The results were compared with the analogous activity of MDP. All compounds tested are strong up-regulators of IL-12 synthesis. All compounds except LK 512 also stimulated IFNgamma synthesis. LK 508, LK 511 and LK 512 are effective in up-regulating IL-2 production. LK 508 and LK 512 considerably up-regulate the synthesis of IL-4 and IL-10. LK 413 and MDP stimulated the production of Th1 promoting and Th1 (IFNgamma and IL-12) cytokines, while LK 508, LK 511 and LK 512 non-selectively up-regulated the production of both Th1 and Th2-types of (IL-4 and IL-10) cytokines. None of the phthalimido-desmuramyl dipeptides was cytotoxic in vitro against the normal cell line HUVEC (human endothelial cells) thereby indicating their potential for use in vivo.