Organic Chemistry Portal
Organic Chemistry Highlights

Monday, January 10, 2011
Douglass F. Taber
University of Delaware

Stereoselective C-O Ring Construction: (+)-Pachastrissamine (Fujii/Ohno), Aspalathin (Minehan), (+)-Varitriol (Ghosh), Aspercyclide A (Spivey), Etnangien (Menche)

(+)-Pachastrissamine (3), also known as Jaspine B, induces apoptosis in melanoma cells by a caspase-dependent pathway. Nobutaka Fujii and Hiroaki Ohno of Kyoyo University developed (J. Org. Chem. 2010, 75, 3831. DOI: 10.1021/jo100544v) a practical route to 3 based on the Pd-mediated cyclization of 1 to 2.

Thomas G. Minehan of California State University, Northridge optimized (Org. Lett. 2010, 12, 1580. DOI: 10.1021/ol100315g) the condensation of 5 with the bis-pivalate 4. This opened a general route to C-aryl glycosides, including Aspalathin (6).

(+)-Varitriol (11) is vinylogously related to 7. A key step in the synthesis of 11 reported (J. Org. Chem. 2010, 75, 2107. DOI: 10.1021/jo100001p) by Subhash Ghosh of the Indian Institute of Chemical Technology was the intermolecular Heck coupling of 8 with 9.

Aspercyclide A (14) and its more stable methyl ether are promising lead compounds for the treatment of asthma. In the course of a synthesis of 14, Alan C. Spivey of Imperial College developed (Chem. Commun. 2010, 1824. DOI: 10.1039/B923528K) the intramolecular Heck cyclization of 12 to 13.

In a bold synthesis of Etnangien (17), Dirk Menche of Ruprecht-Karls-Universitšt Heidelberg showed (J. Org. Chem. 2010, 75, 2429. DOI: 10.1021/ja9056163) that the intramolecular Heck coupling of 15 to 16 proceeded efficiently. The substituents on 15 may be favoring conformations that lead to cyclization.

D. F. Taber, Org. Chem. Highlights 2011, January 10.