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.