. 2020 Feb 11;25(4):770. doi: 10.3390/molecules25040770
© 2020 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/).
Scheme 3.
Synthesis of target compounds 17, 19 and 22.