Cyclogregatin, a new metabolite from Aspergillus panamensis.

During the course of the isolation of gregatin A (1) from submerged cultures of Aspergillus panamensis a new tetronic acid derivative was obtained. According to its cyclic structure this compound was named cyclogregatin (2). In the following the structural elucidation and the biological activities of 2 in comparison with gregatin A will be described. A. panamensis, CBS120.45, was cultivated as described previously0. The crude extract from the culture filtrate was purified by means of chromatography on silica gel. With CHC13 Me2CO (98 :2) gregatin A and cyclogregatin were eluted together. Separation of the two compounds was achieved by rechromatography on silica gel with CH2C12 as eluant. The isolation of cyclogregatin was monitored by TLC on silica gel with toluene Me2COAcOH(70 : 30 : 1) and spraying with vanillin H2SO4 (orange color). Cyclogregatin was obtained as a colorless solid, mp 150155°C, it is soluble in MeOH, Me2C0 and CHC13 and poorly soluble in water. The physico-chemical data of cyclogregatin, C15H18O4, are summarized in Table 1. Similar to the gregatins1'2^ its XHNMRspectrum shows signals for a 1,3-hexadienyl side chain and a