We are grateful to the Spanish Ministerio de Educacion y
Ciencia, as well as to Generalitat Valenciana and
University of Alicante, for their continuous financial
support.

Enantioselective direct aldol reaction: the blossoming of modern organocatalysis

Diverse Methods for Medium Ring Synthesis

This review covers the progress made in the chemistry, synthesis and biology of carbasugars until May 2004. It includes the extensively studied carbapyranoses as well as the scarcely considered carbafuranoses. Specific topics discussed include the natural occurrence of carbasugars, biosynthesis and biological activity of carbasugars, conformational analysis of carbasugars, and the compilation of synthetic methods of carbafuranoses and carbapyranoses.

Synthesis and conformational and biological aspects of carbasugars.

The synthesis of carbocyclic eight-membered rings

Catalysis and synthesis are intimately linked in modern organic chemistry. The synthesis of complex molecules is an ever evolving area of science. In many regards, the inherent beauty associated with a synthetic sequence can be linked to a certain combination of the creativity with which a sequence is designed and the overall efficiency with which the ultimate process is performed. In synthesis, as in other endeavors, beauty is very much in the eyes of the beholder.† It is with this in mind that we will attempt to review an area of synthesis that has fascinated us and that we find extraordinarily beautiful, namely the combination of catalysis and sigmatropic rearrangements in consecutive and cascade sequences.

Toward a Symphony of Reactivity: Cascades Involving Catalysis and Sigmatropic Rearrangements

Total Synthesis of the Cembranoid Diterpene Lactone (+)-Cleomeolide. Some Remarkable Conformational Features of Nine-Membered Belts Linked in 2,6-Fashion to a Methylenecyclohexane Core

Two-carbon intercalation. 4-Cyclooctenones by tandem application of double-Tebbe and Claisen reactions

2-Cyclohexenone rings that form part of a larger structural assembly are amenable to peracid oxidation with formation of an epoxy lactone. These intermediates are readily transformed under acidic, basic, or neutral conditions to ring-contracted aldehydo lactones, which are then subjected to condensation with a slight excess of Tebbe reagent. These conditions result in methylenation of carbonyl groups and set the stage for operation of a Claisen rearrangement. When the latter is catalyzed by Tribal, the sigmatropic process occurs at room temperature. With systems typified by 17 and 24, the isomerization is complete within 15 min. The presence of a proximate angular methyl group as in 9b, 29, and 37 exerts a retarding kinetic effect. In such examples, a period of 6 h is required to achieve completion. Swern oxidation completes the conversion to the 4-cyclooctenones, where the two carbons stemming from the Tebbe reagent are inserted between the original carbonyl and α-olefinic carbons. The overall process is...

Ring expansion by tandem double Tebbe–Claisen technology

Enantioselective synthesis of (+)-cleomeolide, the structurally unique diterpene lactone constituent of Cleome viscosa

Total Synthesis of the Cembranoid Diterpene Lactone (+)‐Cleomeolide. Some Remarkable Conformational Features of Nine‐Membered Belts Linked in 2,6‐Fashion to a Methylenecyclohexane Core.

Christophe M. G. Philippo

Papers

Total Synthesis of the Cembranoid Diterpene Lactone (+)-Cleomeolide. Some Remarkable Conformational Features of Nine-Membered Belts Linked in 2,6-Fashion to a Methylenecyclohexane Core

Two-carbon intercalation. 4-Cyclooctenones by tandem application of double-Tebbe and Claisen reactions

Ring expansion by tandem double Tebbe–Claisen technology

Enantioselective synthesis of (+)-cleomeolide, the structurally unique diterpene lactone constituent of Cleome viscosa

Total Synthesis of the Cembranoid Diterpene Lactone (+)‐Cleomeolide. Some Remarkable Conformational Features of Nine‐Membered Belts Linked in 2,6‐Fashion to a Methylenecyclohexane Core.