New Insights into Rifamycin B Biosynthesis: Isolation of Proansamycin B and 34a-Deoxy-rifamycin W as Early Macrocyclic Intermediates Indicating Two Separated Biosynthetic Pathways.

Abstract

Proansamycin B, the formerly postulated intermediate of rifamycin B biosynthesis, was isolated from cultures of the Amycolatopsis mediterranei mutant F1/24. The structure was determined using UV, IR, NMR and MS techniques. Biotransformation studies demonstrate that proansamycin B is an intermediate of a shunt pathway, a 8-deoxy variant, of rifamycin B biosynthesis leading to 8-deoxy-rifamycin B as the final product.In addition, 34a-deoxy-rifamycin W, the direct precursor of rifamycin W, could be isolated representing the earliest macrocyclic intermediate obtained so far in the biosynthetic route to rifamycin B. Furthermore, the new rifamycin W-28-desmethyl-28-carboxy and rifamycin Whemiacetal, intermediates in, the transformation sequence of rifamycin W to rifamycin S, were isolated. Application of proton NMR measurements (double resonance and ROESY experiments) on the latter compound indicated that the stereochemistry at the chiral center C-28 is R.

Salinisporamycin, a novel metabolite from Salinispora arenicora

“…These results showed a structural resemblance to the ansa chain of rifamycin antibiotics. 10 These assignments are summarized in Figure 2.…”

“…These results were supported by the finding that the IR and UV spectra showed characteristic absorption bands at 1496 cm À1 (1465 cm À1 of 3) and wavelengths at 319 and 408 nm (315 and 410 nm of 3), indicating the presence of a chromophoric system in the naphthoquinone form. 10,12 In addition, the IR spectrum showed a characteristic absorption band at 1600 cm À1 (1606 cm À1 of 3), indicating the presence of a naphthoquinone carbonyl group linked in the intramolecular hydrogen bond. 12 The naphthoquinone ring system of 1 was established by the 13 C NMR spectral data and HMBC correlations in solvent DMSO-d 6 (Table 3, Figure 5).…”

“…Compound 3 did not show cytotoxic activity against A549 cells at 200 mg ml À1 . 10,12,14 Among all rifamycin antibiotics, 1 showed cytotoxic activity. 14 The antimicrobial activity of 1 was tested against six microorganisms by paper disk methods.…”

“…Therefore, bioactive products were isolated from YM23-082 extracts using LC-MS methods. The results showed hat saliniketals A (2) 8,9 and rifamycin S (3) 10 were isolated from YM23-082 extracts. In salinisporamycin (1), it was expected that the ansa chain partial structure could be assigned as saliniketals 8,9 and connected to the naphthoquinone ring system.…”

A cybernetic model to predict the effect of freely available nitrogen substrate on rifamycin B production in complex media

“…For estimating rifamycin B, the broth was mixed 1:1 with butanol and shaked for 4 h at room temperature (150 rpm). After centrifugation (10 min; 5,000×g) the butanol phase was separated and 100-μl sample was used for HPLC analysis (Stratmann et al 2002). Glucose was analyzed via RI detector on HPLC (Hitachi, Merck KgaA, Darmstadt, Germany) using HP-Aminex-87-H column (Biorad, Hercules, CA, USA) at 60°C with a mobile phase of 5 mM sulphuric acid (Ross and Chapital 1987).…”