3.1.4. Benzophenones Derivatives

Benzophenones (BPs) are widely distributed NPs possessing a diphenyl ketone moiety [51]. Given the presence of the chemically active carbonyl group, which can efficiently

react with a variety of functional groups, diverse novel skeletons such as isobenzofuran, isoindolinone, and 3-dihydro-1H-indene, etc., could be formed. There are 12 members of BPs that are discovered from mangrove-associated fungi.

Four unusual 2,3-dihydro-1H-indene isomers, diaporindenes A–D (**39**–**42**) (Figure 13), and an unusual isoprenylisobenzofuran A (**43**) were isolated from *Diaporthe* sp. SYSU-HQ3, a fungus obtained from the branches of the mangrove plant *Excoecaria agallocha* collected from Zhuhai in Guangdong province, China [52]. Compounds **39**–**42** feature a 2,3-dihydro-1H-indene ring and a 1,4-benzodioxan moiety. Isoprenylisobenzofuran A (**43**) represented the first example of an isoprenylisobenzofuran nucleus possessing a rare 1,4-benzodioxan moiety. Biosynthetically, compounds **39**–**43** could be derived from co-occurrence benzophenone type metabolites such as tenellone B, which is formed by acetyl-CoA and malonyl-CoA through the catalysis of PKSs [53] (Scheme 5). In a bioassay, compounds **39**–**43** were found to exhibit significant inhibitory effects against nitric oxide production with IC50 values from 4.2–9.0 *μ*M and selective index (SI) values from 3.5 to 6.9.

**Figure 13.** Structures of compounds **39**–**43**.

**Scheme 5.** Proposed biosynthetic pathway for compounds **39**–**43** [53].
