New bhimamycins from Streptomyces sp. AK 671

Abstract

From the wild-type strain Steptomyces sp. AK 671, three nitrogen-containing octaketides were isolated, bhimamycins F, H and I, besides the known azaanthraquinone utahmycin A and polyketide shunt products SEK 4, SEK 4b, mutactin, dehydromutactin and EM18. The structures were characterized by MS and NMR experiments. The hitherto unknown absolute configuration of the two enantiomers of EM18 was determined by online-CD spectroscopy and quantum-chemical CD calculations. Bhimamycins H and I show weak antibacterial activities, whereas the enzyme phosphodiesterase 4 is strongly inhibited by bhimamycins H and I, which has never been reported for nitrogen-containing octaketides. In addition, bhimamycin H inhibits the enzyme glycogen synthase kinase-3β.

Iridium- and Rhodium-Catalyzed Directed C–H Heteroarylation of Benzaldehydes with Benziodoxolone Hypervalent Iodine Reagents

“…13 C NMR (101 MHz, CDCl3) δ 195.2, 160.4, 145.4, 138.8, 131.5, 126.0, 123.4, 122.9, 121.5, 113.7, 111.5, 110.7, 103.6. Spectra data differs slightly from the values reported in literature 5.…”

“…Following a reported procedure, 5 phosphoryl trichloride (0.400 mL, 4.30 mmol, 1.20 equiv.) was slowly added to DMF (2 mL) at 15 °C under Ar.…”

Involvement of the Baeyer–Villiger Monooxygenase IfnQ in the Biosynthesis of Isofuranonaphthoquinone Scaffold of JBIR‐76 and ‐77

“…JBIR‐76 and ‐77 are isofuranonaphthoquinone (IFNQ) derivatives that were isolated from Streptomyces sp. RI‐77 (Scheme ); a broad range of IFNQs have been isolated from a wide variety of organisms, including plants and actinomycetes (Scheme ) . Some of these IFNQ derivatives have been reported to have interesting biological properties, including antioxidant and antiplasmodial activities .…”

Biscogniauxone, a New Isopyrrolonaphthoquinone Compound from the Fungus Biscogniauxia mediterranea Isolated from Deep-Sea Sediments

“…This inference also was supported by the HR-TOF-MS results and indicates the presence of an N atom in the molecule of 1 . Only few known compounds possess the N -containing isopyrrolonaphthoquinone structures, such as azamonosporascone [12], bhimamycin C and D [13] as well as bhimamycin F, H, and I [14]. According to the established data (Figure 3, Table 1), compound 1 was identified as a new N-atom-containing isopyrrolonaphthoquinone compound named biscogniauxone.…”

“…This effect is much lower in comparison to the GSK inhibitor TDZD-8. However, it is of interest that another isopyrrolonaphthoquinone, namely bhimamycin H, also inhibited the activity of this enzyme in a similar range (IC 50 value of 18 μM) [14]. Therefore, isopyrrolonaphthoquinones and similar structures can be considered as possible candidates for the development of drugs in order to treat diseases related to the biological target GSK-3β, such as diabetes type 2, neurological disorders, or cancer [19,20,21].…”