. 2016 Feb 4;21(2):189. doi: 10.3390/molecules21020189
© 2016 by the authors.
Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons by Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).
Scheme 1.
Synthetic pathways for compounds 2–18.