Highly substituted carbocyclic seven-membered rings are frequently found in natural products and their synthesis represents a significant challenge to the synthetic chemist. Direct intramolecular cyclization of these systems often proves difficult and this fact has catalyzed the development of a variety of strategies based on a convergent intermolecular cycloaddition strategy. This concept article discusses the major cycloaddition approaches utilized to access these types of structures and primarily focuses on examples employed in the synthesis of natural products.

The cycloaddition strategy for the synthesis of natural products containing carbocyclic seven-membered rings.

The application discloses methods of treating mammalian diseases characterized by undesirable angiogenesis by administering estradiol derivatives including those comprising colchicine or combretastatin A-4 structural motifs of the general formulae found below in a dosage sufficient to inhibit cell mitosis. The application discloses novel compounds used in the methods.

Estrogenic compounds as anti-angiogenesis agents

Ein neues Jahrtausend hat begonnen – Grund genug, sich die Frage zu stellen, welchen Stand die Totalsynthese von Naturstoffen erreicht hat. Dieser Aufsatz mochte eine Antwort geben, indem er die Entwicklung dieser chemischen Disziplin, die Aspekte von exakter Wissenschaft und schoner Kunst in sich vereint, von Anbeginn bis in die heutige Zeit beschreibt; es wird geschildert, wie viel wir in der Wissenschaft der Totalsynthese schon erreicht haben, aber auch, dass dieses Forschungsgebiet den Kinderschuhen gerade erst entschlupft.

Der Stand der Totalsynthese zu Beginn des 21. Jahrhunderts

Critical review on medicinally potent plant species: Gloriosa superba

Recent advances in siloxane-based aryl-aryl coupling reactions : focus on heteroaromatic systems

Total syntheses of (&)-desacetamidoisoolchicine (2b) and (&)-colchicine (la) have been achieved. Key features of the synthetic sequence are the facile incorporation of a tropolone dication equivalent via ketone 6 and introduction of the 7-acetamido group. Some of the mechanistic details of the conversion of alcohol 7 to dihydrotropolone 8 and alcohols 14a,b to ester 19 are discussed. Colchicine (la), one of the major alkaloid constituents of the

S. P. Tanis

Papers

Convergent total synthesis of (.+-.)-colchicine and (.+-.)-desacetamidoisocolchicine