A New Tricyclic Undecose Nucleoside from Streptomyces scopuliridis RB72

Experimental Section

General Procedures. The high resolution electrospray ionization (HRESI) and electron impact (EI) mass spectra were obtained using a Q-Tof micro LC-MS/MS instrument (Waters, USA) and CP3800-1200L (Varian, USA) mass spectrometer, respectively. 1H-NMR (nuclear magnetic re-sonance) and 13C-NMR spectra were recorded on a Bruker (Rheinstetten, Germany) AM 300, AMX 500 and AMX 800 NMR spectrometer using TMS as an internal standard. Column chromatography was performed using a silica gel (Kieselgel 60, 70-230 mesh, Merck, Darmstadt, Germany) and Lichroprep RP-18 (40-63 mm, Merck). Thin layer chromatography (TLC) analysis was performed on Kieselgel 60 F254 plates (silica gel, 0.25 mm, Merck) and spots were detected by examination with a UV lamp Spectroline Medel ENF-240 C/F (Spectronics Corporation, Westbury, NY) followed by the addition of 10% H2SO4 reagent. Solvents and reagents were obtained from commercial sources and used without further purification. Unless otherwise noted, all chemicals were purchased from Sigma.

Fermentation, Extraction and Isolation. The Strepto-myces scopuliridis RB72 was cultivated in Bennet’s medium 80 L, [160 × 500 mL: yeast extrac (0.5 g), beef extract (0.5 g), N-Z amine type A (Sigma C0626, 1.0 g), glucose (5.0 g), agar (7.5 g), distilled water (0.5 L), autoclave at 121 °C for 15 minutes] for 10 days at 27 °C and then filtered with celite 545 (from Samchun Pure Chemical Co., Ltd). The filtrates were concentrated (121.4 g), passed through a diaion HP-20 (Adsorbent resin from Mitsubish Co., Ltd) column (15 cm × 50 cm), and washed with H2O (5.0 L) followed by MeOH (5.0 L). The MeOH extract was evaporated to dryness in vacuo and then the crude extract (22.1 g) was subjected to reversed phase C-18 (from Merck) flash chromatography (5 cm × 50 cm) using the solvent systems of H2O and MeOH with a 10% increase of MeOH to yield six fractions (MeOH/H2O = 50/50, 60/40, 70/30, 80/20, 90/10, and 100/0). The 60% MeOH fraction was separated by reversed phase HPLC (25 × 4.6 mm, 5 μm, 2 mL/min) by eluting the 35% H2O and 65% MeOH solvents to produce a mixture at a retention time of 9 min. For purification, the mixture was rechromato-graphed by using the 40% ACN and 60% H2O solvents to give compound 1 (9 mg) and compound 2 (704 mg). Similarly, the 70% MeOH fraction was separated with the 30% H2O and 70% MeOH solvents to yield compound 3 (54 mg). Finally, compound 4 (14 mg) was isolated from the 80% MeOH subfraction by using the 25% H2O and 75% MeOH solvents

Herbicidin K (1): An amorphous powder : +0.13 (C 0.2, CH3OH), has the molecular formula C22H27N5O10 de-duced by a high-resolution electrosprayionization time-of-flight mass spectrometry (HRESITOFMS) experiment (found at m/z [M+H]+) 522.1849, calculated for C22H28N5O10 522.1836). 1H and 13C-NMR pectra data are presented in Table 1.