Immunomodulatory constituents from three ascomycetes, Gelasinospora heterospora, G-multiforis, and G-longispora

Three new 2-pyrones (2H-pyran-2-ones) called multiforisins G (3), H (1), an d I (4), and a known hexaketide sordarial (2) have been isolated from an As comycete Gelasinospora heterospora. Among them, 1, 2, and 3 have been prove d to be the immunosuppressive components of the fungus. Compounds 1, 3, and 4 have also been isolated from G.multiforis together with multiforisin A ( 5), which was formerly isolated from this fungus as its main immunosuppress ive feature, and 1-5 have also been isolated from G. longispora. The absolu te stereostructure of 2, which was not previously certain, has finally been determined to be (3'R,4'S). It has been found that the multiforisins 1, 3, and 5 in which one of the two substituents at positions 3 and 5 is a hydro xymethyl group and the other is a formyl or an acetoxymethyl group, show hi gh immunosuppressive activity; the immunosuppressive activity of 3 does not seem to be due to inhibition of interleukin 2 (IL-2) production.