![Chemical structures of Oxazolidinones
N-[[(5S)-3-(3-fluoro-4-morpholin-4-
ylphenyl)-2-oxo-1,3-oxazolidin-5-
yl]methyl] acetamide
Linezolid C16H20FN3O4
(5R)-3-[3-fluoro-4-[6-(2-methyltetrazol-5-
yl)pyridin-3-yl]phenyl]-5-(hydroxymethyl)-1,3-
oxazolidin-2-one
Tidezolid C17H15FN6O3](https://image.slidesharecdn.com/group3finalupdate-250204172932-dd725068/85/Macrolides-and-polypeptides-Group-3-final-update-pptx-22-320.jpg)
Macrolides and polypeptides, Group 3 final update.pptx
- 1. Group 3 Macrolides, Oxazolidinones & polypeptides PRESENTERS • ATEKANIZA DOREEN VU-BPC-2307-O886-DAY • BALIKUDEMBE JOSEPH VU-BPC-2307-0912-DAY • NAMBUULE LYDIA VU-BPC-2307-0516-DAY
- 2. Macrolides Macrolides are a group of antibiotics produced by various strains of Streptomyces. Picromycin was the first to be identified as macrolide compound, erythromycin and carbomycin were later reported as new antibiotics. And then later other macrolides. They are made up of a large macrocyclic lactone ring and one or more deoxy sugars, notably cladinose and General Structure of Macrolides
- 3. Are used to treat infections caused by gram-positive bacteria and some gram-negative bacteria
- 4. Chemical structures of macrolides Erythromycin C37H67NO13 Azithromycin C38H72N2O12
- 6. At C2: As macrolide are unstable in acidic pH, a number of stratergies have been utilized to improve the acidic stability of erythromycin – fluorination of erythromycin At C9, the addition of hydroxylamine to the ketone to form oxime eg roxythromycin. At C6, Alteration of C6 hydroxyl group: nucleophilic functionality which initiates erythromycin degradation. The azalides (azithromycin) are semi synthetic 15 membered congeners in which a nitrogen atom has been introduced to expand a 14 membered precursor leads to an extended spectrum of action
- 7. Structure activity relationship Macrolide ring ❑erythromycin core structure is a 14 membered lactone ring called erythronolide . ❑this macrocyclic structure is essential for binding to the bacterial ribosome. ❑Substitutions :- alkyl, hydroxyl, or amino groups at C-4,C-6, OR C-8 positions can enhance activity
- 8. Sugar moieties • Erythromycin has two sugar molecules attached to the lactone ring L cladinose : at position 3 essential for the activity against gram positive bacteria this sugar enhance the binding affinity to the ribosome Desosamine : at position 5 important for activity against gram-negative bacteria Other sugar ( e.g mycarose , forosamine ) these are also responsible for enchancing the stability and activity.
- 9. • Functional group • The presence of hydroxyl group (-OH) and keto group (=O) on the lactone ring are critical for the antibiotic activity. • Position ;- hydroxyl group at C-2’ , C-4’ and C-6’ positions essential • These group interact with the 23S ribosomal RNA in the 50S subunit of bacteria inhibit protein synthesis. • Ester group Formation :- lactonization essential for macrolide ring formation Substitution :- alkyl or aryl esters can enhance activity
- 10. Intramolecular attack to the ketone group
- 12. Synthesis of macrolides (chloramphenicol)
- 13. Mechanism Of Action Of Macrolide Antibiotics Macrolides binds with 50s ribosomal subunit Inhibits peptide transferase activity Interferes with translocation of growing peptides from A to P site. Inhibits protein synthesis
- 14. macrolides • Typically bacteriostatic activity • Bactericidal at high concentrations • Erythromycin chloramphenicol and clindamycin all bind to 50s ribosome and the 3 may antagonize each others activity because they compete for the same binding site • There combination should be avoided
- 15. • Therapeutic Application • The macrolides are used for the treatment of upper and lower respiratory tract and soft-tissue infections primarily caused by Gram-positive microorganisms like Streptococcus pyogenes and Streptococcus pneumoniae, Legionnaire's disease, prophylaxis of bacterial endocarditis by Streptococcus viridians. • They are also used in upper and lower respiratory tract infections caused by Haemophilus influenzae, mycoplasmal pneumonia. • In combination with rifabutin, macrolides are used in Mycobacterium avium complex infections in patients with AIDS. • It also finds some use for certain sexually transmitted diseases, such as gonorrhea and pelvic inflammatory disease, caused by Chlamydia trachomitis.
- 16. Therapeutic indications of macrolides Erythromycin • Respiratory Tract Infections: Community-acquired pneumonia, bronchitis, and sinusitis. • Skin and Soft Tissue Infections: Cellulitis and erysipelas. • Sexually Transmitted Infections: Chlamydia and non-gonococcal urethritis. • Atypical Infections: Legionnaires’ disease and Mycoplasma pneumonia. • Prophylaxis: Rheumatic fever
- 17. Oxazolidinone antibiotics Oxazolidinones are synthetic antibiotics that inhibit bacterial protein synthesis by preventing the formation of the 70S initiation complex. Are used to treat serious infections caused by gram- positive bacteria, including those resistant to other antibiotics Examples: Linezolid, Tedizolid, Deplazolid
- 18. Mechanism of action of Oxazolidinones •Binding to the Ribosome: Oxazolidinones bind to the 23S ribosomal RNA of the 50S subunit of the bacterial ribosome. •Inhibition of Protein Synthesis: They inhibit the peptidyl transferase activity, which is crucial for the elongation of the protein chain. This prevents the addition of new amino acids to the growing peptide chain. •Prevention of Initiation Complex Formation: Oxazolidinones prevent the formation of the 70S initiation complex, which is necessary for the start of protein synthesis. •Resistance Mechanisms: Bacteria can develop resistance through mutations in the 23S rRNA or ribosomal proteins, and acquisition of resistance genes (cfr and cfr-like, optrA, and poxtA) often associated with mobile genetic elements
- 19. Therapeutic indications of Oxazolidinones Linezolid • Skin and Soft Tissue Infections: Including complicated and uncomplicated infections. • Community-Acquired Pneumonia: In both adults and children. • Nosocomial Pneumonia: Pneumonia that occurs 48 hours or more after hospitalization. • Infections Caused by Gram-Positive Bacteria: Such as Staphylococcus aureus (including MRSA), Streptococcus, and Enterococcus (including VRE). • Bacteremia: Bloodstream infections. • Bone and Joint Infections: Including osteomyelitis and septic arthritis. • Infections Caused by Mycobacterium tuberculosis: Including multidrug-resistant tuberculosis. • Infections Caused by Nocardia species: Including nocardiosis
- 20. Therapeutic indications of Oxazolidinones Tedizolid • Complicated Skin and Soft Tissue Infections: Including those caused by MRSA. • Community-Acquired Pneumonia: In adults. • Nosocomial Pneumonia: Pneumonia that occurs 48 hours or more after hospitalization
- 21. Structural classification & variations 5-membered ring containing nitrogen and oxygen (2-oxazolidinone) Core Structure: 2-oxazolidinone ring Substituents: The ring typically has substituents at the C5 position, which can vary among different oxazolidinones. e.g. Linezolid has phenyl group, a morpholine moiety & An acetamide group at the 5-position of the oxazolidinone ring. Tedizolid has A fluorine atom on the phenyl ring, A 2- methyltetrazol-5-yl group attached to the pyridine ring & A hydroxymethyl group at the 5-position of the oxazolidinone ring Deplazolid has these substituents: A fluorine atom on the phenyl ring, 1-methyl-5,6-dihydro-1,2,4- triazin-4-yl group attached to the phenyl ring & A hydroxymethyl group at the 5-position of the oxazolidinone ring.
- 22. Chemical structures of Oxazolidinones N-[[(5S)-3-(3-fluoro-4-morpholin-4- ylphenyl)-2-oxo-1,3-oxazolidin-5- yl]methyl] acetamide Linezolid C16H20FN3O4 (5R)-3-[3-fluoro-4-[6-(2-methyltetrazol-5- yl)pyridin-3-yl]phenyl]-5-(hydroxymethyl)-1,3- oxazolidin-2-one Tidezolid C17H15FN6O3
- 23. Summarized SAR for Oxazolidinones
- 24. SAR of Oxazolidinones cont.. • 5-Substituent on Oxazolidinone Ring: Acetylaminomethyl Group: This group is considered optimal for antibacterial activity. Hydroxymethyl or Halogenomethyl Groups: These groups generally show weaker antibacterial activity. Thiocarbonyl Sulfur: Replacing carbonyl oxygen with thiocarbonyl sulfur enhances antibacterial activity • C- and D-Rings: Optimization: Modifications in the C- and D-rings that interact with conserved regions of the peptidyl transferase center binding site enhance potency. Hydroxymethyl or 1,2,3-Triazole Groups: These groups retain activity against linezolid-resistant strains. Acetamide Substituents: These reduce potency against resistant strains
- 25. SAR of Linezolid •Core Structure: The oxazolidinone core is essential for the antibacterial activity of linezolid. Modifications to this core can significantly impact its efficacy. •Substituents: The presence of specific substituents on the oxazolidinone ring, such as the fluorine atom at the 3-position and the hydroxyl group at the 5-position, are crucial for binding to the bacterial ribosome and inhibiting protein synthesis. •Stereochemistry: Linezolid contains chiral centers, and its stereochemistry is important for its activity. The (S)-enantiomer is more active than the (R)-enantiomer. •Lipophilicity: The lipophilic nature of linezolid enhances its ability to penetrate bacterial cell membranes, which is important for its antibacterial activity. •Resistance: The SAR of linezolid also helps in understanding resistance mechanisms. Mutations in the bacterial ribosome can reduce the binding affinity of linezolid, leading to resistance.
- 26. chemical synthesis of linezolid • Formation of the Oxazolidinone Core: • Starting Materials: The synthesis begins with ethyl 2-aminomethyl-3- methylbutanoate and chloroacetyl chloride. • Reaction: These two react to form an intermediate ethyl 2- (chloroacetamido)-3-methylbutanoate. • Cyclization: The intermediate undergoes cyclization in the presence of a base (e.g., triethylamine) to form the oxazolidinone core. • Introduction of the R1 Group: • R1 Group: The R1 group in Linezolid is a methyl group. • Reaction: The oxazolidinone core is treated with methyl iodide to introduce the methyl group at the appropriate position.
- 27. Introduction of the R2 Group: R2 Group: The R2 group in Linezolid is a benzyl group. Reaction: The oxazolidinone core with the R1 group is then reacted with benzyl bromide to introduce the benzyl group. Final Steps: Purification: The final product, Linezolid, is purified through crystallization or other suitable methods. Characterization: The synthesized Linezolid is characterized using techniques like NMR, IR, and mass spectrometry to confirm its structure.
- 28. Stepwise chemical synthesis of linezolid
- 29. Polypeptides Polypeptide drugs are a diverse group of medications that have complex polypeptide structure that contain lipid moieties beside amino acids. They include; antibiotics, hormones, and other therapeutic agents
- 30. Polypeptide antibiotics Polypeptide antibiotics, such as bacitracin and polymyxin B, work by disrupting bacterial cell membranes, leading to cell death. •Bacitracin: Disrupts bacterial cell wall synthesis by inhibiting the dephosphorylation of lipid carriers. •Polymyxin B: Interacts with the bacterial cell membrane, leading to increased permeability and cell death. •Colistin (Polymyxin E): Similar to Polymyxin B, it disrupts the cell membrane of Gram-negative bacteria. •Actinomycin D: Binds to DNA and inhibits RNA synthesis, which is why it's used in cancer chemotherapy
- 31. Therapeutic indication of polypeptide antibiotics •Bacitracin A: Primarily used topically for superficial skin infections caused by Staphylococcus aureus. •Polymyxin B: Used for infections caused by Gram-negative bacteria, such as Pseudomonas aeruginosa and Acinetobacter species. It's often reserved for cases where other treatments are ineffective. •Colistin (Polymyxin E): Indicated for severe infections caused by multi- drug resistant Gram-negative bacteria, including Pseudomonas aeruginosa and Acinetobacter species. It's typically used when other antibiotics are not effective
- 32. Chemical structures of polypeptide antibiotics Bacitracin A C66H103N17O16S Actinomycin D C62H86N12O16
- 33. Chemical structures of polypeptide antibiotics Polymixin B C56H98N16O13 Colistin C56H98N16O13
- 34. Mechanism of action • Bacitracin • Only member in Bacitracin • It is bacteriostatic in nature but may be bactericidal depending on the antibiotic concentration and the susceptibility of the specific organisms. • It inhibits incorporation of amino acids and nucleotides into the cell wall hence interferes with the final dephosphorylation step in the phospholipid carrier cycle. • This causes impedance of mucopeptide transfer from cytoplasm to the growing cell wall.
- 35. Polymyxins • Polymyxin B • Colistin (polymyxin E) • Bind to phospholipids in the gram negative bacterial cell membrane with a detergent like action • and they damage the cell membrane function. • They are non selective on bacterial membrane
- 36. Glycopeptides • Vancomycin • Active on Gram positive bacteria and inhibits cell wall synthesis. • This is achieved by binding to peptide precursors in the bacterial cell wall preventing cross linking of peptidoglycan side chains.
- 38. Vancomycin • Glycopeptide with cyclic heptapeptide backbone • The cyclic structure gives stability and resistance to enzymatic degradation • It bonds with hydrogen on the D Ala terminus of the peptidoglycan precursors • It has aromatic rings that stacks with bacterial target • It has activity only on gram positives and no activity on gram negatives due to its larger molecular structure • It can not enter through porin proteins and its highly lipophobic cant pass across the phospholipid outer membrane.
- 39. Vancomycin
- 40. Bacitracin • It is a complex mixture of at least 10 polypeptides (A, A1, B, C, D, E, F1, F2, F3, and G), of which bacitracin A fraction is the most abundant and the most potent. A divalent ion Zn++ enhances its activity.
- 41. Antimicrobial Peptides (AMPs) • Antimicrobial Peptides (AMPs): AMPs are typically short peptides, usually between 12 to 50 amino acids in length. They are characterized by: • Positive charge: Rich in lysine, arginine, and histidine residues. • Hydrophobicity: Contain a high proportion of hydrophobic residues. • Secondary structure: Can form α-helices, β-sheets, or extended structures. • They are small peptides that exhibit broad-spectrum antimicrobial activity. • They disrupt bacterial cell membranes, leading to cell lysis, and can also modulate the immune response.
- 42. Classification of AMPs on the basis of various criteria. (A) Based on gene encoding pattern (Data-mining strategy). (B) Significant cellular or thermodynamic criteria. (C) Subdivision of positively charged (cationic) AMPs.
- 43. Examples of AMPS • Defensins Source: Humans and many other organisms Structure: β-Stranded with disulfide bonds Action: Defensins insert themselves into microbial membranes and create channels that disrupt the integrity of the membrane. Example: Human β-defensin 2 (HBD-2) is effective against bacteria like Staphylococcus aureus and Escherichia coli, as well as fungi like Candida albicans. • Cathelicidins Source: Humans and many other animals Structure: Linear, α-Helical Action: Cathelicidins disrupt microbial membranes, but they also have immunomodulatory functions, such as attracting immune cells to infection sites. Example: LL-37, the only cathelicidin found in humans, is effective against bacteria, fungi, and viruses, including methicillin-resistant Staphylococcus aureus (MRSA).
- 44. Nisin Source: Bacteria, specifically Lactococcus lactis Structure: Cyclic peptide with unusual amino acids Action: Nisin binds to bacterial cell wall precursors, preventing cell wall synthesis and causing cell death. Example: Nisin is used as a food preservative to prevent the growth of harmful bacteria like Listeria monocytogenes in dairy products. Pleurocidins Source: Fish, specifically winter flounder (Pleuronectes americanus) Structure: α-Helical Action: Pleurocidins disrupt bacterial membranes and have broad-spectrum antimicrobial activity. Example: Pleurocidin has been shown to be effective against pathogens like Vibrio cholerae and Staphylococcus aureus.
- 45. Histatins Source: Human saliva Structure: Linear, rich in histidine residues Action: Histatins disrupt fungal cell membranes and inhibit fungal enzymes. Example: Histatin 5 is particularly effective against Candida albicans, a common cause of oral thrush
- 46. • Histatins Source: Human saliva Structure: Linear, rich in histidine residues Action: Histatins disrupt fungal cell membranes and inhibit fungal enzymes. Example: Histatin 5 is particularly effective against Candida albicans, a common cause of oral thrush.
- 47. Summarized Mechanism of Action of AMPS •Membrane Permeabilization: AMPs can disrupt microbial cell membranes, leading to cell death.e.g Cathelicidins •Transmembrane Channel Formation: Some AMPs form pores in the microbial membrane, causing ion leakage and cell death. E.g Difensins, •Immune Modulation: AMPs can enhance the immune response by acting as immunomodulators e.g. Cathelicidins
- 48. Structure of LL- 37 Cathelicidin
- 49. Structures Histatin 5 (C133H195N51O33) Pleurocidin (C129H192N36O29)
- 50. chemical synthesis of LL-37 by Microwave- Assisted Solid-Phase Peptide Synthesis (SPPS) •Peptide Synthesis: The synthesis begins with the assembly of the peptide chain using standard SPPS techniques. The amino acids are sequentially added to a solid support, typically a resin, using coupling reagents like DIC/OxymaPure. •Microwave Assistance: Microwave irradiation is used to accelerate the coupling reactions, especially for difficult sequences. This method improves the efficiency and yield of the synthesis. •Segmentation Approach: For longer peptides like LL-37, a segmentation approach is often employed. This involves synthesizing smaller segments of the peptide and then coupling them together. •Purification and Characterization: The synthesized peptide is purified using techniques like HPLC and characterized using mass spectrometry (MS) and analytical High-Performance Liquid Chromatography (HPLC) to confirm its identity and purity. •Antibacterial Testing: The synthesized LL-37 is tested for its antimicrobial activity to ensure it retains its biological function
- 51. chemical synthesis of Histatin 5, by solid- phase peptide synthesis (SPPS) • Peptide Assembly: The amino acids are sequentially added to a solid support (resin) using coupling reagents like DIC/OxymaPure. • Deprotection and Activation: Each amino acid is deprotected and activated before the next one is added. • Cleavage: The synthesized peptide is cleaved from the resin. • Purification: The crude peptide is purified using techniques like HPLC. • Characterization: The final product is characterized using mass spectrometry (MS) and analytical HPLC to confirm its identity and purity.