Cytotoxic Dihydrothiophene-Condensed Chromones from the Marine-Derived Fungus Penicillium oxalicum

Abstract

Two new dihydrothiophene-condensed chromones and a new natural chromone, namely oxalicumones A-C (1-3), respectively, were isolated from a culture broth of a marine-derived fungus, Penicillium oxalicum. The structures of 1-3 and acetylated derivatives of 1 (4-7) were elucidated on the basis of spectroscopic methods and chemical reactions. The absolute configuration of 1 and 2 were established by using the modified Mosher ester method and circular dichroism data of an in situ formed [Rh2(OCOCF3)4] and [Mo2(OAc)4] complex. (R)-MTPA ester of 1 showed cytotoxicity against A375, SW-620, and HeLa carcinoma cell lines with IC50 values of 8.9, 7.8, and 18.4 µM, respectively. Compound 1 displayed cytotoxicity against A375 and SW-620 cell lines with IC50 values of 11.7 and 22.6 µM, respectively. The structure-biological activity relationship of 1 was discussed.

Chemistry of α-Oxoesters: A Powerful Tool for the Synthesis of Heterocycles

“…Friedel−Crafts reaction of substituted aromatic compounds with ethyl oxalyl chloride was developed using AlCl 3 under solvent-free conditions to give the corresponding arylglyoxalates in 80−91% yields (entry 2). 17 Rhodium-catalyzed reaction of ethyl cyanoformate with arylboronic acids in the presence of H 3 BO 3 in dioxane, at room temperature for 30 min, and then at 60°C for 3 h, led to the corresponding ethyl arylglyoxalates in 46−87% yields (entry 3). 18 Carbonylation of aryl iodide using 70 atm initial pressure of CO catalyzed with PdCl 2 (Cy 3 ) 2 in the presence of alcohols and Et 3 N in DCM at 70°C afforded arylglyoxalates in 22−69% yields (entry 4).…”

“…(1.2 equiv) using 0.2 equiv of Et 3 N in refluxing toluene for 5 min, then at room temperature for 3 h, followed by acetylation of obtained nitro alcohol with Ac 2 O (1.5 equiv) in the presence of DMAP (0.2 equiv) at 0°C to room temperature for 4 h. By treatment of acetylated nitro alcohol product with tosylmethyl isocyanide (TosMIC, 1 equiv) and DBU (2 equiv) in CH 3 Quiclet-Sire et al 104 have reported radical reaction between N-ethylsulfonylenamide 158 and α-xanthyl ketones 159 to give pyrrole-2-carboxylates 162. N-Ethylsulfonylenamide 158 was prepared by reaction of ethyl pyruvate with ethanesulfonamide in the presence of POCl 3 in anhydrous acetonitrile under reflux conditions for 4 h, and then reacted with xanthate 159 using AIBN (2.5 mol %) in a mixture of heptane and chlorobenzene (5/1: v/v) under reflux conditions and argon atmosphere.…”

“…Reactions were conducted in anhydrous THF at 50−60°C for 7 h, and gave corresponding triazoles 241 in 17−28% yields, which were converted to [1,2,3]triazolo[1,5-a]quinoxalin-4(5H)-ones 242 when hydrogenated in the presence of Pd/C or Ni-Raney in EtOH or EtOH/water at room temperature, respectively.…”

Endophytes in the plant Huperzia serrata: fungal diversity and discovery of a new pentapeptide

“…3). P. oxalicum has been widely isolated from other plants, e.g., coffee plant (Vega et al 2006) and the south China sea gorgonian (Sun et al 2012). P. oxalicum could be used as a biocontrol agent against Fusarium wilt of tomato (Larena et al 2002) and has a great capacity to degrade chitin (Pareek et al 2013), cellulose, and poly (ε-caprolactone) (Li et al 2012).…”

“…P. oxalicum could be used as a biocontrol agent against Fusarium wilt of tomato (Larena et al 2002) and has a great capacity to degrade chitin (Pareek et al 2013), cellulose, and poly (ε-caprolactone) (Li et al 2012). Additionally, P. oxalicum is a good source of natural products such as oxalicumones A-C (Sun et al 2012) and ochratoxin A (Vega et al 2006). However, there are no reports on the isolation of Dragendorff-positive compounds or peptides from P. oxalicum.…”