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. 2022 May 24;31(7):1224–1239. doi: 10.1007/s00044-022-02890-2

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© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2022

This article is made available via the PMC Open Access Subset for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.

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Scheme 3 — Reagents and conditions: HCOOH, r.t. 12 (64%); Ac₂O, DMAP, CH₂Cl₂, r.t., 13 (82%); EDC, DMAP, CH₂Cl₂, r.t., 14 (24%), 15 (77%), 16 (87%), 17 (52%), 18 (38%), 19 (42%), 20 (41%), 21 (32%), 22 (90%), 23 (71%), 24 (51%), 25 (95%), 26 (87%), 27 (89%)