ChemInform Abstract: Marine Terpenes and Terpenoids. Part 19. Structure of a Tetracyclic Norcembranolide Derivative Isolated from the Soft Coral Sinularia dissecta.

Abstract

Marine Terpenes and Terpenoids. Part 19. Structure of a Tetracyclic Norcembranolide Derivative Isolated from the Soft Coral Sinularia dissecta. --(KOBAYASHI, M.; RAO, K. M. CH. A.; KRISHNA, M. M.; ANJANEYULU, V.; J.

Polycyclic Furanobutenolide-Derived Cembranoid and Norcembranoid Natural Products: Biosynthetic Connections and Synthetic Efforts

“…In a similar fashion, the related furanobutenolide-derived norcembranoids, including ineleganolide ( 9 ), 20 horiolide ( 21 ), 38 kavaranolide ( 22 ) 39 all possess a central heptacycle (Figure 5). Comparatively, the majority of the remaining members of the polycyclic furanobutenolide-derived norcembranoids including dissectolide ( 23 ), 40 sinulochmodin C ( 10 ), 21 scabrolide B ( 24 ), 15 scabrolide A ( 25 ), 15 yonarolide ( 26 ), 41 and 12-hydroxyscabrolide A ( 27 ) 42 are all constructed around a central 6-membered carbocycle with a cycloheptanone ring decorating the peripheral structure. The final members of this family of polycycles are sinulanorcembranolide A ( 28 ) 43 and 1-epi-sinulanorcembranolide A ( 29 ), 44 which also contain a cycloheptanone on the outer reaches of the carbocyclic scaffold, but contrastingly possess a unique polycyclic scaffold containing a transannular cyclopentenone with a flanking, bridged hydroxylactone.…”

“…Two plausible biosynthetic routes for the formation of dissectolide A ( 23 ) have been postulated (Scheme ). − ,, The core [7,6,5,5]-tetracyclic structure bears remarkable similarity to the mandapamate and plumarellide cembranoids (see Scheme ), perhaps suggesting that intermediate 45 , with the Δ 13,14 bond in the trans configuration, undergoes a [4 + 2] cycloaddition with the C(6)–C(7) enol tautomer of the dihydrofuranone ring to directly construct the central cyclohexene moiety of tetrahydrofuran 46 . Macrocycle 45 could alternatively proceed to intermediate furan 46 in a stepwise manner through a Michael addition between C(7) and C(11) and subsequent vinylogous aldol cyclization of the resultant enolate to construct the C(14)–C(6) bond.…”

“…Two plausible biosynthetic routes for the formation of dissectolide A (23) have been postulated (Scheme 8). [1][2][3]24,40 The core [7,6,5,5] The final members of the polycyclic furanobutenolide-derived norcembranoid diterpenes discovered to date are sinulanorcembranolide (28) 43 and 1-epi-sinulanorcembranolide (29), 44 which contain a novel [7,5,6]-carbocyclic core that is flanked by a bridging lactone. In the most plausible biosynthetic route, sinulanorcembranolide ( 28) is proposed to derive from 5- episinuleptolide (5) after a retro-oxa-Michael addition to form enone 47 (Scheme 9A).…”

Sinudenoids A–E, C19-Norcembranoid Diterpenes with Unusual Scaffolds from the Soft Coral Sinularia densa

“…The main structural feature of this type of diterpene generally is the lack of a C-18 methyl linked at C-4 in comparison with C 20 -cembranoids. In previous studies, some unusual carbon skeletons such as 5/5/7/6 tetracyclic ineleganolide, 5/5/6/7 tetracyclic sinulochmodin C, and dissectolide A, 5/6/5/7 tetracyclic sinulanorcenbranolide A, and dimeric norcembranoidal sinulochmodin A were reported. They were thought to originate from the common C 19 -norcembranoid diterpene precursor, norrubifolide, through different cyclization processes. , …”

Pharmacophore-Directed Retrosynthesis Applied to Rameswaralide: Synthesis and Bioactivity of Sinularia Natural Product Tricyclic Cores

“…Soft corals belonging to the genus Sinularia produce a number of cembranoid and norcembranoid diterpenes bearing a complex, caged, highly oxygenated tri- or tetracyclic skeleton as seen in several representative members 1 – 6 (Figure ). − However, the limited availability of these natural products from corals has hindered a broader understanding of their bioactivity. To date, moderate cytotoxicity of ineleganolide ( 5 ) toward the P388 leukemia cell line (11.6 μM ED 50 ) was reported.…”