. 2018 Jul 30;23(8):1901. doi: 10.3390/molecules23081901
© 2018 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 (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Figure 13.
The key steps in the synthesis of 18.