Isolation of the New ( - ) - ( 3 / ? , 4 S ) - 4 - Hydroxymellein from the

The fungus Septoria ( Phaeosphaeria) nodorum Berk is a common parasite of wheat. It is responsi­ ble for a fungal disease which seriously affects crops (septoriosis). This fungus produces in cul­ tures a series of highly potent phytotoxins which were previously investigated. Thus, we reported on the isolation of (-)-(3i?)-m ellein (ochracin) (4) [1], (3 7?)-0-methylmellein, ( )-(3 R, 4 7?)-4-hydroxymellein (5), (-)-(3 7?)-7-hydroxymellein, mycophenolic acid [2], septorine [3], N-methoxyseptorine [4], and N-methoxyseptorinol [5]. Undoubted­ ly, the observed phytotoxic activity of this fungus is due to the summation of these various metabo­ lites, some of them being endowed of a particularly strong biological activity. Mellein was shown to produce an important reduction in C 0 2 net assimi­ lation and an increase in stomatal resistance in seedling leaves of wheat [6-10]. In the present publication, the isolation of the new isomer (-)-(3 R ,45) (6) from the culture medi­ um of this fungus is reported. The results so far ob­ served are discussed in relationship with the fact