A pair of new isocoumarin epimers from soil fungus Hypoxylon sp.

Abstract

In our research on novel secondary metabolites from micro-organisms, two new (1-2) and four known dihydroisocoumarins (3-6) were derived from soil fungus Hypoxylon sp. Their structures were determined with extensive NMR data analysis and ECD calculation comparing with those of experimental CD spectra. Interestingly, compounds 1 and 2 possessed the same planar structure and very similar NMR data, suggesting 1 and 2 were a pair of epimers at either C-3 or at C-4, confirmed by the totally opposite cotton effect around 250 nm in the CD spectra of 1 and 2. Moreover, for the first time, we revealed that the CD absorption peak at 250 nm was dominated by C-3 orientation, rather than the orientation of C-3 substituents, by intensive ECD investigations.

Dihydroisocoumarins from Radix Glycyrrhizae

“…The Heteronuclear Multiple-Bond Correlation (HMBC) spectrum (Fig. 2 ) showed the long-rang correlations between H-7 at δ H 6.99and C-8a at δ C 108.2, C-5 at δ C 124.7, C-8 at δ C 161.1; between H-6 at δ H 7.64 and C-10 at δ C 62.2, C-8a at δ C 108.2, C-4a at δ C 141.3; between H-10 at δ H 5.09/5.17 and C-5 at δ C 124.7, C-4a at δ C 141.3, C-11 at δ C 170.8, between H-9 at δ H 1.45 and C-4 at δ C 62.3, between H-4 at δ H 4.66 and C-3 at δ C 78.5, C-4a at δ C 141.3, C-5 at δ C 124.7, between H-4 at δ H 4.66 and C-5 at δ C 124.7, which led to a conclusion that the planar structure of compound 1 was similar to that of (3 R , 4 R )-4,8-dihydroxy-5-(hydroxymethyl)-3-methylisochroman-1-one [ 6 ], except for the acetylated of hydroxyl groups at C-10. Thus, the planar structure of 1 was determined as shown in Fig.…”

Recent advances in the discovery, biosynthesis, and therapeutic potential of isocoumarins derived from fungi: a comprehensive update

“…It is worth mentioning that none of the obtained compounds was tested for any relevant biological activity. 149…”

The Novel Compounds with Biological Activity Derived from Soil Fungi in the Past Decade

“…The two new compounds are assigned as (3 R , 4 R )-4,8-Dihydroxy-5-(hydroxymethyl)-3-methylisochroman-1-one 418 and (3 R , 4 S )-4,8-dihydroxy-5-(hydroxymethyl)-3-methylisochroman-1-one 419 . 133 Two new epimeric dihalogenated diaporthins, (9 R *)-8-methyl-9,11-dichlorodiaporthin 420 and (9 S *)-8-methyl-9,11-dichlorodiaporthin 421 ( Figure 5B ), have been isolated from the soil fungus Hamigera fusca NRRL 35721. 134 Chemical characterization of ethyl acetate extract of Exophiala sp.…”