Leptosperols A and B, Two Cinnamoylphloroglucinol–Sesquiterpenoid Hybrids from Leptospermum scoparium: Structural Elucidation and Biomimetic Synthesis

Abstract

Leptosperols A and B (1 and 2), two cinnamoylphloroglucinol–sesquiterpenoid hybrids featuring unprecedented 1-benzyl-2-(2-phenylethyl) cyclodecane and 2-benzyl-3-phenylethyl decahydronaphthalene backbones, along with their biosynthetic precursor (3), were isolated from Leptospermum scoparium. Compounds 1 and 2 represent the first example of phloroglucinol derivatives biogenetically constructed by a De Mayo reaction. The biomimetic synthesis of leptosperol B (2) was achieved using the proposed biosynthetic pathway. In addition, compounds 1 and 2 showed significant anti-inflammatory effects in zebrafish acute inflammatory models.

Antibacterial Triketone‐Phloroglucinol‐Triketone Adducts fromMyrtus communis

“…This observation together with the HMBCs between HÀ C(9) and C(1)/ C(3)/C(8) as well as the molecular formula information suggested that the bicyclic triketone unit was connected with the phloroglucinol group via C(8)À C(9) and C(1) À OÀ C(3) bonds to form a dihydropyran ring. The correlations between HÀ C(21) and HÀ C(18)/HÀ C (19) as well as between HÀ C (17) and HÀ C(23) in the NOESY spectrum indicated that HÀ C(17) was on the β-face of molecule and the isopropyl unit and the furan ring were on the α-face ( Figure 3). The lack of optical activity demonstrated that 1 was racemic.…”

“…Previous investigations has resulted in the identification of some phloroglucinol derivatives with antibacterial activities from this plant [4,11–13] . Over the course of our ongoing effort to obtain bioactive and structure unique constituents from Myrtaceae plants, [14–19] three pairs of new triketone‐phloroglucinol‐triketone adducts with an rare polycyclic ketal skeleton, myrtucyclitones A–C ((+)‐ and (−)‐ 1 – 3 ), ( Figure 1) were obtained from the title plant. Their structures and absolute configurations were determined by NMR analysis and chemical calculations.…”

Dimeric Acylphloroglucinol Derivatives with New Skeletons from Leptospermum scoparium

“…Meanwhile, phloroglucinols could couple with terpenes, triketones or other phloroglucinols to construct more complex natural products, which exhibited cytotoxic, [4] anti‐inflammatory, [5] antiviral, [6] and antimicrobial [7–8] effects. In a search for structurally unique and biologically interesting natural products from family Myrtaceae, our group had reported a series of novel phloroglucinol derivatives with multiple biological activities [9–14] …”

Cajuputones A–C, β‐Triketone Flavanone Hybrids from the Branches and Leaves of Melaleuca cajuputi

“…[6 -9] Recent years, the discovering of diverse β-triketone-terpene hybrids form Myrtaceae family has made Melaleuca genus be a hot spot in natural products research field. [10][11][12][13] Melaleuca cajuputi (previous name: Melaleuca leucadendron) was a widely cultivated landscape plant in southern China and was native to Australia (tea tree). The leaves and barks of M. cajuputi are used as a traditional Chinese medicine to treat inflammatory wounds and rheumatic arthralgia.…”

“…Besides many monoterpene constituents found in the essential oil, [3–5] phytochemical investigations of Melaleuca species have also revealed many nonvolatile secondary metabolites, including β ‐triketone, flavonoids, triterpenoids, and tannins [6–9] . Recent years, the discovering of diverse β ‐triketone‐terpene hybrids form Myrtaceae family has made Melaleuca genus be a hot spot in natural products research field [10–13] …”