. 2019 Oct 23;24(21):3816. doi: 10.3390/molecules24213816
© 2019 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 3.
Chemical structures of compound 15–18.