A new metal-free oxidative radical [2+2+1] carbocyclization of benzene-linked 1,n-enynes with two C(sp(3))H bonds adjacent to the same heteroatom is described. This method achieves two C(sp(3))H oxidative functionalizations and an annulation, thus providing efficient and general access to a variety of fused five-membered carbocyclic hydrocarbons.

Metal-Free Radical [2+2+1] Carbocyclization of Benzene-Linked 1,n-Enynes: Dual C(sp3)-H Functionalization Adjacent to a Heteroatom

An asymmetric catalytic decarboxylative [4+2] annulation of 4-ethynyl dihydrobenzooxazinones and carboxylic acids has been established by cooperative copper and nucleophilic Lewis base catalysis. A C1 ammonium enolate and copper–allenylidene complex, each catalytically generated from different substrates, underwent a cascade asymmetric propargylation and lactamization process to yield optically active 3,4-dihydroquinolin-2-one derivatives with excellent levels of stereoselectivity (up to 99 % ee, 95:5 d.r.).

Asymmetric [4+2] Annulation of C1 Ammonium Enolates with Copper-Allenylidenes.

Stereoselective reactions of nitro compounds in the synthesis of natural compound analogs and active pharmaceutical ingredients

A palladium-catalyzed vinylcyclopropane (3+2) cycloaddition approach to the Melodinus alkaloids.

The first stereoselective synthesis of epimeloscine has been accomplished in 13 total steps with a longest linear sequence of 10 steps. The core of the synthesis takes only five steps, the key ones being acylation, stereoselective tandem radical cyclization of a divinylcyclopropane to make two rings, and group-selective ring-closing metathesis of the resulting divinylcyclopentane to make the last ring.

/pdf/a-short-total-synthesis-of-epimeloscine-and-meloscine-3w8q696x4i.pdf

A short total synthesis of (±)-epimeloscine and (±)-meloscine enabled by a cascade radical annulation of a divinylcyclopropane.

For the alkaloids meloscine, epimeloscine and scandine, isolated from the Apocynacee Melodinus scandens FORST., the structures 1, 10 and 11, respectively, are deduced. Scandine is proved to possess the relative configuration as shown in 11 r. For meloscine and epimeloscine the relative configurations as depicted in 1 r and 10 r are discussed.

Die Konstitution der Melodinus‐Alkaloide (+)‐Meloscin, (+)‐Epimeloscin und (+)‐Scandin. 1. Mitteilung über Alkaloide aus Melodinus scandens FORST

The alkaloid (−)-laurepukine is shown to possess one of the epimeric N-oxide structures 4 or 5. Oxidation of (−)-pukateine (3) by hydrogen peroxide gives (−)-laurepukine and, as a second product, 6-epi-laurepukine.

Ek. Weiss

Papers

Die Konstitution der Melodinus‐Alkaloide (+)‐Meloscin, (+)‐Epimeloscin und (+)‐Scandin. 1. Mitteilung über Alkaloide aus Melodinus scandens FORST

Notiz zur Konstitution des Laurepukins. 8. Mitteilung über natürliche und synthetische Isochinolin-Derivate†‡

Alkaloide aus melodinus scandens forst. 1. mitt. konstit. der melodinus-alkaloide (+)-melosin, (+)-epimeloscin und (+)-scandin

Natuerliche und synthetische isochinolin-derivate 8. mitt. konstitution des alkaloids laurepukins

Glykoside und aglykone 322. mitt. cardenolide und pregnanderivate aus wurzeln von trachycalymma fimbriatum (weimarek bullock)