. 2012 Dec 6;17(12):14464–14483. doi: 10.3390/molecules171214464
© 2012 by the authors;
licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).
Scheme 5.
Synthetic pathways for compounds 18–22a,b.