The first asymmetric synthesis of the sesquiterpene quinones 3-oxo- and 3β-hydroxytauranin (1, 2) was achieved and the originally proposed structure of 3α-hydroxytauranin was revised. The protected benzyl chloride 5 was obtained in six steps starting from 4-bromo-3,5-dihydroxybenzoic acid (8) via a highly scalable approach. The troublesome Negishi coupling of the benzyl chloride 5 with alkenyldimethylalane 6 was optimized to furnish all-trans-farnesylarene 14 in very good yield. This prenylated arene was transformed in six additional steps to 3β-hydroxytauranin (2). Finally, a new convenient access to propargylated terpenes without using dry cryogenic ammonia and gaseous allene or propyne is described.

Rove beetles of the genus Stenus produce and store bioactive alkaloids like stenusine (3), 3-(2-methylbut-1-enyl)pyridine (4), and cicindeloine (5) in their pygidial glands to protect themselves from predation and microorganismic infestation.

The biosynthesis of stenusine (3), 3-(2-methylbut-1-enyl)pyridine (4), and cicindeloine (5) was previously investigated in Stenus bimaculatus, Stenus similis, and Stenus solutus, respectively. The piperideine alkaloid cicindeloine (5) occurs also as a major compound in the pygidial gland secretion of Stenus cicindeloides. The three metabolites follow the same biosynthetic pathway, where the N-heterocyclic ring is derived from L-lysine and the side chain from L-isoleucine. The different alkaloids are finally obtained by few modifications of shared precursor molecules, such as 2,3,4,5-tetrahydro-5-(2-methylbutylidene)pyridine (1). This piperideine alkaloid was synthesized and detected by GC/MS and GC at a chiral phase in the pygidial glands of Stenus similis, Stenus tarsalis, and Stenus cicindeloides.

The two new indole alkaloids 2-amino-1,5-dihydro-5-(1H-indol-3-ylmethyl)-4H-imidazol-4-one (1), 2-amino-5-[(6-bromo-1H-indol-3-yl)methyl]-3,5-dihydro-3-methyl-4H-imidazol-4-one (2), and auramine (3) have been isolated from the sea anemone Heteractis aurora. Both indole alkaloids were synthesized for the confirmation of the structures. Homarine (4), along with uracil (5), hypoxanthine (6), and inosine (7) have been obtained from Octopus cyanea.

A Ti^III-mediated radical cyclization cascade has been used for the synthesis of the sesquiterpenes (+)-albicanol, (+)-drimanol, and (+)-drimanic acid. Starting from all-trans-farnesol, (+)-albicanol could be prepared in seven steps in an overall yield of 14.9 %. Furthermore, a highly diastereoselective hydrogenation of (+)-albicanol to give (+)-drimanol has been developed. We used the synthesized (+)-drimanic acid to achieve the first synthesis of the marine sesquiterpene hydroquinone deoxyspongiaquinol and the quinone deoxyspongiaquinone. Thus, this synthetic strategy gave access to five natural products.

The monoterpene lilac aldehyde (=2-(5-ethenyl-5-methyloxolan-2-yl)propanal) is a widespread flower scent. Lilac aldehyde is emitted in high amounts from nocturnal plant species, and it is highly attractive to nocturnal moth pollinators, such as Hadena bicruris, the pollinating seed predator of Silene latifolia. Lilac aldehyde possesses three stereogenic centers and can occur in eight stereoisomers which induce different antennal responses in H. bicruris. The distribution pattern of stereoisomers differs among plant species, and if H. bicruris has different receptors for detecting different isomers, it may use these differences to discriminate flowers of S. latifolia hosts from flowers of non-host plants. To investigate the question whether the moths have in their antennae one olfactory receptor or several different receptors for the detection of the single lilac aldehyde isomers, (2S,2′S,5′S)-lilac aldehyde was diastereoselectively synthesized. (2S,2′S,5′S)-Lilac aldehyde and its isomeric mixture were tested electrophysiologically on antennae of H. bicruris. The results displayed antennal responses, which are characteristic for a single receptor that detects the different lilac aldehyde isomers.

The new piperideine alkaloid cicindeloine (3) was isolated from the pygidial glands of the beetles Stenus cicindeloides and Stenus solutus. The structure and absolute configuration of 3 were elucidated by NMR spectroscopy and asymmetric synthesis, respectively. A very efficient gram-scale synthesis of 3 was developed using an intramolecular aza-Wittig reaction as the final step. The synthetic route is comprised of 12 steps and proceeds in 20 % total yield. Nine of the 12 steps were conducted without column chromatography.

All the stereoisomers of stenusine (1) and norstenusine (21) have been efficiently synthesized by the asymmetric hydrogenation of pyridines. The (2R,3S)- and (2R,3R)-isomers of 1, that are difficult to prepare, have been synthesized for the first time using a chemoenzymatic approach in eight steps with an 8 % total yield. All the target compounds were obtained in good stereochemical purity by using very simple and inexpensive reagents and auxiliaries.

The new cembrane diterpene (3E,11E)-cembra-3,8(19),11,15-tetraene-7α-ol (1), nephthenol (2), and all-trans-peridinin (3) have been isolated from the soft coral Litophyton arboreum. The tetraterpene 3, (+)-7,8-epoxy-7,8-dihydrocembrene C (4), emblide (5), sarcophytoxide (6), sarcoglaucol-16-one (7), guajacophine (8), and 1,4-peroxymuurol-5-ene (9) have been obtained from the soft coral Sarcophyton ehrenbergi. The compounds were characterized primarily by NMR spectroscopy. Some of the terpenes were tested for their antiproliferative activity against the cell lines HUVEC and K-562 and for cytotoxicity against the cell line HeLa, and they showed moderate activities.

Four new acetoxycapnellenes 1–4, the first epoxyprecapnellene 5, along with the known dihydroxycapnellene 6 and monoacetoxycapnellene 7, have been isolated from the soft coral Dendronephthya rubeola. The structures were determined primarily by NMR spectroscopy. The compounds 6 and 7 showed a good antiproliferative activity against the cell line L-929 (murine fibroblasts) and a good cytotoxic activity against the HeLa (human cervix carcinoma) cell line. Compound 6 strongly inhibits the interaction of the oncogenic transcription factor Myc with its partner protein Max. Myc/Max-Interaction inhibitors are therapeutically interesting compounds in oncology.

The new cembranoid diterpene danielid (1) along with 3α-ethoxyfuranocembranoid 2, pukalide (3), 13α-acetoxypukalide (4), furanocembranoid 5, and furanosesquiterpene 6 have been isolated from the soft coral Sinularia asterolobata. The furanocembranoid diterpene 11β,12β-epoxypukalide (7) and the sesquiterpene (−)-bicyclogermacrene (8) have been obtained from the soft coral Litophyton arboreum. The structures were elucidated primarily by NMR spectroscopy. The furanocembranoids 2, 4, and 5 show good antiproliferative activities against the cell lines L-929 and K-562, and weak cytotoxic effects on HeLa cells.