Nucleosides and Nucleotides

Abstract

The naturally occurring nucleoside and nucleotide antibiotics exist as either the C ‐ or N ‐glycosides. They include ezomycin A 1 (C 26 H 38 N 8 O 15 S), ezomycin B 1 (C 26 H 39 N 7 O 17 S), ezomycin C 1 (C 26 H 37 N 7 O 16 S), ezomycin A 2 (C 19 H 26 N 6 O 12 ), ezomycin B 2 (C 19 H 25 N 5 O 13 ), ezomycin C 2 (C 19 H 25 N 5 O 13 ), showdomycin (C 9 H 11 NO 6 ), isoshowdomycin (C 9 H 11 NO 6 ), maleimycin (C 7 H 7 NO 3 ), oxazinomycin (C 9 H 11 NO 7 ), pyrazomycin (pyrazofurin) (C 9 H 13 N 3 O 6 ), formycin (C 10 H 13 N 5 O 4 ), formycin B (C 10 H 12 N 4 O 5 ), oxoformycin B (C 10 H 12 N 4 O 6 ). These antibiotics contain a variety of purine and pyrimidine rings. The naturally occurring nucleoside/nucleotide antibiotics, which have been isolated from bacteria, fungi, blue‐green algae, and marine sponges, have proven to be useful biochemical probes in eucaryotic, procaryotic, viral, fungal, and plant systems. The purine nucleosides inhibit protein synthesis, RNA and DNA synthesis, and methyltransferases; they have antimycoplasmal, antiviral, hypotensive, antifungal, antimycobacterial, and antitumor activities and induce sporulation. The pyrimidine nucleosides inhibit protein synthesis, virus replication, RNA and DNA synthesis, and cAMP phosphodiesterase. The imidazole nucleosides inhibit nucleic acid synthesis. The diazepin nucleosides inhibit adenosine deaminase (ADA). The indole nucleosides inhibit bacteria, yeast, fungi, and viruses. The N ‐nucleotide antibiotics include agrocin 84 (C 21 H 34 N 6 O 16 P 2 ), thuringiensin (C 22 H 30 N 5 O 19 P), phosmidosine (C 16 H 24 N 7 O 8 P), fosfadecin (C 13 H 19 N 5 O 10 P 2 ), and fosfocytocin (C 12 H 20 N 4 O 13 P 2 ). Thuringiensin, produced by B. thuringiensis , is a β‐exotoxin that exerts its toxic action on insects and mammals through the inhibition of RNA polymerases. Phosmidosine inhibits pore formation of Botrytis cinerea and Aspergillus niger . Fosfadecin and fosfocytocin inhibit gram‐positive and gram‐negative bacteria.