... Tetrahedron Letters. ... For synthesis of 5, see: (b) Mohanta, PK; Kim, K. Tetrahedron Lett.2002, 43, 3993; (c) Lee, SH; Kim, SI; Park, JG; Lee, ES; Jahng ... For review on 5 and related compounds, see (f) Bergman, J. In The Alkaloids, Chemistry and Pharmacology; Brossi, A., Ed.; Vol. ...