Tricyclic Sesquiterpenes from Marine Origin

Abstract

The structure elucidation, biosynthesis, and biological activity of marine carbotricyclic sesquiterpene compounds are reviewed from the pioneering results to the end of 2015. Their total syntheses with a particular emphasis on the first syntheses, enantiomeric versions, and syntheses that led to the revision of structures or stereochemistries are summarized. Overall, 284 tricyclic compounds are classified into fused, bridged, and miscellaneous structures based on 54 different skeletal types. Tricyclic sesquiterpenes constitute an important group of natural products. Their structural diversity and biological activities have generated further interest in the field of drug discovery research, although the exact mechanisms of action of these species are not well known. Furthermore, these tricyclic structures, according to their chemical complexity, are a source of inspiration for chemists in the field of total synthesis for the development of innovative methodologies.

Rumphellolide J, an Ester of 4β,8β-Epoxycaryophyllan-5-ol and Rumphellaoic acid A, from the Gorgonian Rumphella antipathies

“…Furthermore, an HMBC correlation between H-5 ( H 4.58), an oxymethine proton, and the C-5 ester carbonyl carbon ( C 178.5) was found, which proved the existence of an ester linkage in 1. [11,12], and the results of a NOESY analysis (Figure 3). The atom configurations of the carbon skeleton (C-1,  C 42.5; C-8,  C 73.1; C-9,  C 36.2; and C-1,  C 49.0; C-4,  C 53.0; C-8,  C 41.7; C-9,  C 46.0) of 1 were found to be similar to those of 2 (C-1,  C 42.4; C-8,  C 72.7; C-9,  C 36.2) [9] and 3 (C-1,  C 48.9; C-4,  C 52.6; C-8, 41.9; C-9,  C 46.0) [11].…”

Computational and Synthetic Investigation of Cationic Rearrangement in the Putative Biosynthesis of Justicane Triterpenoids

“…[7] Similar decalin rearrangements by activation of the C1 position have been employed in small molecule synthesis, [8] and the bicyclo-[5.3.0]decane motif is widely observed in natural products. [9] However, these decalin rearrangements have been reported to undergo competitive alkyl migrations, [10,11] which prompted us to consider whether the formation of 2 might compete with the formation of 1 . A detailed understanding of the reaction mechanism would aid in rationally employing this and other cationic rearrangement tactics in organic synthesis.…”

The Invention of New Methodologies: An Opportunity for Dating Natural Products

“…This linear triquinane natural product is a marine sesquiterpene of the capnellane family, isolated from Capnella imbricata. 29 In this approach, we thus…”