. 2018 Aug 21;23(9):2092. doi: 10.3390/molecules23092092
© 2018 by the author.
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/).
Scheme 3.
Synthesis of compounds 15a–c, 17a–c and 20.