Synthesis of the indeno[1,2-]indole core of janthitrem B.

The tetracyclic core structure of the majority of indole diterpenoids features a -hydrindane moiety that is fused to an indole unit. We report here a novel synthetic route that includes a photo-Nazarov cyclization of a 3-acylindole precursor initially providing the thermodynamically preferred -hydrindanone. After reduction and conversion to the cyclopentadiene, dihydroxylation and hydrogenation provided the indoline.

Biomimetic Synthesis of Cyanogramides B and C.

Marinacarboline E and cyanogramides B and C from the marine-derived bacterium have been synthesized. The key step is the Baeyer-Villiger oxidation of marinacarboline E to a ketene aminal via O → N acetyl migration, followed by addition of water or MeOH. Replacing the phenylethyl by a styryl side chain afforded dehydromarinacarboline E that was oxidized to a tetracyclic aminal.

Aza-BODIPY Route to Ageladine A.

The marine natural product ageladine A was synthesized by exploiting novel aza-BODIPY-type boron complexes that allowed the regioselective dibromination of the pyrrole unit, as confirmed by quantum chemical calculation (ωB97XD/TApr-cc-pVDZ). The parent tricycle was accessed by Suzuki-Miyaura cross-coupling employing Buchwald's precatalyst. The boron complex of ageladine A exhibited strong fluorescence that was greater than that of the natural product by a factor of ∼30 and that disappeared in the presence of 2-azido groups.

Incorporation of -HMBC and NOE Data into Computer-Assisted Structure Elucidation with WebCocon.

Over the past decades, different software programs have been developed for the Computer-Assisted Structure Elucidation (CASE) with NMR data using with various approaches. WebCocon is one of them that has been continuously improved over the past 20 years. Here, we present the inclusion of 4J correlations (4J-HMBC) in the HMBC interpretation of Cocon and NOE data in WebCocon.

Synthesis of (-)-Dihydroraputindole D by Enantioselective Benzoylation of a 1,3-Diol Intermediate.

The enantioselective synthesis of (-)-dihydroraputindole D is reported. The key step is the desymmetrizing benzoylation of a prochiral 1,3-diol employing Trost's ProPhenol catalyst system, which has been applied for the first time to a cyclic molecule carrying geminal hydroxymethyl groups. The cyclopenta[f]indoline system was assembled by Au(I)-catalyzed cyclization of an alkynylated indoline precursor.