. 2021 Jul 12;26(14):4230. doi: 10.3390/molecules26144230
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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 (https://creativecommons.org/licenses/by/4.0/).
Scheme 2.
Synthetic approaches to 1, part two.