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. 2023 Oct 6;28(19):6954. doi: 10.3390/molecules28196954

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© 2023 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 (https://creativecommons.org/licenses/by/4.0/).

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Scheme 16 — Synthetic pathway of calixcephems 151 (Ceph. X) and 152 (Ceph. V) and their corresponding single cephems 153 (Ceph. X) and 154 (Ceph. V) [158]. BSU: N,N′-bis(trimethylsilyl)urea, Py: pyridine.