Appropriately substituted nonracemic allyl alcohols, readily prepared from the corresponding enones by application of the CBS methodology, were converted to optically active cycloheptenone derivatives with almost complete transfer of chirality via an efficient “one-pot”, cycloisomerization/Claisen rearrangement process. This methodology was directly applied to the expedient total synthesis of (−)-frondosin B.

The title complex Co(Mespyr)Cl is prepared from CoCl and (Mespyr)H. Instead of the expected (Mespyr)CoCl complex, a complex with formula (Mespyr)CoCl is isolated wherein the angle strain of the Mespyr ligand results in metal ligation by only two of the three ligand donor atoms. Careful examination of structural, spectroscopic, and magnetic features indicates this compound is best described as a complex of high-spin Co(II) with a neutral radical ligand.

Rings with 7 or more members Q 0050Asymmetric Synthesis of Seven-Membered Carbocyclic Rings via a Sequential Oxyanionic 5-Exo-Dig Cyclization/Claisen Rearrangement Process. Total Synthesis of (-)-Frondosin B. -The method includes the preparation of chiral allyl alcohols using the Corey-Bakshi-Shibata protocol followed by a microwave-assisted tandem cyclization/rearrangement. Bicyclic cycloheptenone derivatives are formed with good yields and nearly complete chirality transfer. Product (IX) is a precursor for the total synthesis of (-)-frondosin B (X). -(OVASKA*, T. V.; SULLIVAN, J. A.; OVASKA, S. I.; WINEGRAD, J. B.; FAIR, J. D.; Org. Lett. 11 (2009) 12, 2715-2718; Dep. Chem., Conn. Coll., New London, CT 06320, USA; Eng.) -R. Steudel 45-062