Embedded medium-sized carbacycles and cyclohepta [b]indoles occur frequently as scaffold elements in natural products and bioactive compounds.Described herein is ac onceptionally novel photochemically triggered cascade process to these scaffolds.K ey to the cascading ring-expansion process is an unprecedented intramolecular alkyne analogue of the de Mayor eaction. Prof. Dr.J.Rehbein FakultätfürChemie und Pharmazie, UniversitätRegensburg 93053 Regensburg (Germany) Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

The ex-chiral-pool synthesis of an advanced gukulenin A precursor from (-)-piperitone is revealed. Key C/C connecting maneuvers to the synthesis of a C dissymmetric bis(α-tropolonic) ether building block are a ring-contracting Meinwald rearrangement, a photochemically triggered two-carbon ring expansion, and a homodimerization by cross-metathesis.

The uncatalyzed intramolecular carbonyl ene (ICE) reaction of substituted ε,ζ-unsaturated α-keto esters to terpenoid-related building blocks has been studied. We found a beneficial effect of a silyl substituent at the ene segment on the kinetics of the ICE reaction. A generalizable and scalable synthesis of ε,ζ-unsaturated α-keto esters from allylic alcohols was developed.

The title compound, C17H24N2O3S, was synthesized in order to determine the relative configuration of the corresponding β-keto aldehyde. In the U-shaped mol­ecule, the five-membered ring approximates an envelope with the methyl­ene atom adjacent to the quaternary C atom being the flap. The dihedral angles between the four nearly coplanar atoms of the five-membered ring and the flap and the aromatic ring are 38.8 (4) and 22.9 (2)°, respectively. The bond angles around the S atom are in the range 104.11 (16)–119.95 (16)°. In the crystal, mol­ecules are linked via N—H⋯O by hydrogen bonds, forming a chain along the a-axis direction.

Embedded medium-sized carbacycles and cyclohepta [b]indoles occur frequently as scaffold elements in natural products and bioactive compounds.Described herein is ac onceptionally novel photochemically triggered cascade process to these scaffolds.K ey to the cascading ring-expansion process is an unprecedented intramolecular alkyne analogue of the de Mayor eaction.